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You may have gotten one or more emails from Mail Delivery Subsystem and wondered what that was about. There are several possibilities for why you have received these emails. In this article, we will explain why you may get email from Mail Delivery Subsystem and what you can do to stop them.

What is Mail Delivery Subsystem

Mail Delivery Subsystem is a name for the mailer daemon that is responsible for delivering your emails.

If you are using Gmail (this doesn’t necessarily mean you’re using an @gmail address), you may get an email from Mail Delivery Subsystem, whose email address is [email protected]. This is an email from google mail itself.

Why does Mail Delivery Subsystem send you emails?

You may get one or more emails from Mail Delivery Subsystem due to a problem with an email you have sent. This message is known as a “bounce message” because instead of being delivered, the email “bounced” back to you. For example, I recently received two Mail Delivery Subsystem emails after sending a couple of calendar invites.

If you have received many of these kinds of emails and you don’t believe you have even sent any of the emails in the first place, you may have a problem. See the How to stop Mail Delivery Subsystem emails section below for more information on how to proceed.

Delivery Status Notification (Failure)

At the top of the email I received was written “Delivery Status Notification (Failure).” This tells me that an email I tried to send failed. In the body of the email was the reason for the failure:

Recipient inbox full Your message couldn't be delivered to [email protected]. Their inbox is full, or it's getting too much mail right now.

It seems my friend’s iCloud storage was full and so they could not receive any emails until they increased their iCloud storage.

Address not found

This is another common message type from Mail Delivery Subsystem. It usually indicates a problem with the address, such as some part of the address being mistyped. Similar messages may have a different wording:

Mailbox unavailable

Unknown user

Unrouteable domain

Host unknown

Message blocked

This means your message was blocked for some reason. This can happen when you add too many recipients to CC or BCC or if you have a “suspicious” looking URL link in your email.

Error codes

The message from Mail Delivery Subsystem may contain an error code. This code can be accompanied by a message. Codes in the 400s usually indicate a temporary issue, and those in the 500s mean that something will need to be done/changed in order for the sender to receive your email. For the email I received, the message was:

The response from the remote server was:

This tells me pretty much the same thing as the message above — Recipient inbox full.

How to stop Mail Delivery Subsystem emails

The way to approach this problem will differ depending on your situation:

If you have only received a few emails

If the following are true:

You have only received a few Mail Delivery Subsystem emails.

The body of the email lists the failure for the same recipient’s email address.

You know you have sent (or tried to) that individual the emails that have failed.

Then the email is most likely legitimate (otherwise, see below). A couple of common problems are:

The recipient’s mail is full

If you see anything in the email message indicating this, then the individual to whom you are trying to send the emails should check with their email provider. They are likely not receiving emails from anyone and need to take action to fix the situation. For example, my friend needed to increase their iCloud storage. If you have no other way to contact the person you are trying to email, you can try to send them a very short email with no attachments, letting them know about the problem. It may or may not go through.

You have the address wrong

If your Mail Delivery Subsystem email indicates that the address, mailbox, user, domain or host is not found, unknown, unavailable or unrouteable, then you need to double-check the email address you are using.

If you received Mail Delivery System emails for mail you didn’t send If you have received a lot of emails

This indicates a problem called mailer daemon spam. There are a couple of possibilities here:

Someone is spoofing your email address and sending lots of spam to other addresses, some of which bounce back to you. In this case, your email account has not been hacked.

Your email account has been hacked, and someone is sending spam to your contacts (or others). This can happen if you gave out your information to a phisher or if you opened an attachment containing malware.

Steps you need to take

If there is a possibility that your email account or your computer has been compromised, you should do the following to stop the problem:

Especially if you are using a PC, you will want to make sure your antivirus/anti-malware software is up to date and running. Scan your computer and follow the suggestions given by your antivirus software.

Change your email password (after running antivirus). Use a secure password that you are not using anywhere else.

If your email account was being used to send phishing/spam to your contacts, you should warn them, or else they may find themselves with the same problem.

If you are using Gmail:

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How To Show Only Unread Emails In The Mail App For Mac

Organizing emails has always been a difficult task for many of us, as the inbox keeps getting cluttered with the emails you receive every day. One way to organize these emails is to manually put them into their appropriate folders or tags so that they are easy to find and manage, but that manual task consumes a great deal of your time.

Many apps and tools have been developed to help you organize your emails so that your inbox does not look cluttered. One of these is the Smart Mailbox feature located in the Mail app on your Mac. The feature lets you create Smart Mailboxes that only contain the emails that pass through the filter criteria set by you.

You can create a Smart Mailbox for only unread emails, and that way you will have all of your unread emails in a separate mailbox and can then work on them from there.

Here’s how to create a Smart Mailbox for your unread emails.

Showing Only Unread Emails in the Mail App

You only need access to the Mail app on your Mac to do the task. You do not need a third-party app.

1. Launch the Mail app.

3. The New Smart Mailbox dialog box should launch for your to enter your filter criteria.

In the name field you can enter a name that fits the smart mailbox. For example, since you are creating a mailbox that will only have unread emails, you can enter the name “Only Unread Emails.”

In the drop-down menu below you need to select the option that says “Message is unread.” What this will do is only add your unread emails to the smart mailbox leaving all other emails aside.

You can now open this mailbox, work through the emails, and after they are read they will be removed from the mailbox. However, they will still appear in your regular inbox.


If you would like for your unread emails to appear separately in the Mail app on your Mac, you can use the Smart Mailbox feature as described above.

Let us know if this helped you organize your emails!

Mahesh Makvana

Mahesh Makvana is a freelance tech writer who’s written thousands of posts about various tech topics on various sites. He specializes in writing about Windows, Mac, iOS, and Android tech posts. He’s been into the field for last eight years and hasn’t spent a single day without tinkering around his devices.

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Search Engine Updates : Spot Them Before They Happen

Search Engine Updates : Spot Them Before They Happen

Over the past few weeks we’ve seen all the major engines update in some form. From major Google updates to minor MSN And Yahoo updates. Sometimes these updates catch website owners off guard.

It wasn’t too long ago that you could set your watch (almost) by a search engine update. And at that time Google was the one most watched. For a few days during the end of the month and spilling into the next month Google would do a complete update of it’s index. Those days are long gone in favor of a constantly updating index, however they do throw in major updates here and there to keep us on our toes.

Similarly, Yahoo! Also does that all inclusive update occasionally. Before I go into the indicators for these two lets take a look at the third of the big 3:

MSN – MSN launched their own crawler based search engine earlier this year. They claim to use a neural network to help index pages and improve results over time.

They also subscribe to the belief of an perpetual update where new content is added as its found, and results are tweaked on the fly.

However, in monitoring MSN since its inception I’ve found occasions where there have been updates which are noticeable. I think I’ve even discovered how you too can watch for them.

Usually, just before a shakeup of MSN’s results, there’s a dramatic change in either pages indexed or back links for a bunch of sites.

Usually I check these factors across all the engines for my clients on Monday mornings, first thing.

And almost without fail, before a major MSN change I will see pages or back links indexed drop from a high number to a low number or even 0. It isn’t the usual change you see in MSN – where new pages or links are added a few at a time. This is a major change in the numbers.

In every case I can think of this precedes a major update by a few days to a week.

In other words, if my client had 15,434 pages indexed, it would drop to 27. This was a precursor to an MSN update. Conversely if the client site went from 15,434 to 15,994 I wouldn’t consider that as an update indication.

Yahoo! – There are a couple indicators for Yahoo! That I’ve noticed in the past.

For one thing, they do something similar to MSN. That is you will see a change in the days leading up to the update. For example, for one of my clients, their back links had remained steady at just under 1 million for the past few weeks. Then in the weeks leading up to the most recent update they began to drop. Now they are at about 760,000 – a 25% loss in back links.

Similarly, the indexed page count followed a similar pattern. For this same client the indexed page count sat around 2.3 million for the past few weeks. 2 weeks before the update it dropped to 1.8 million then to 1.5 million the next week. Now it’s back up to just under 2.3 million.

One other thing I’ve noticed with Yahoo! is that they seem to plan major updates every 3-6 months and these updates take place either just before or just after their earnings report.

I’ve noticed this for the past couple years now and for a few updates you could almost gauge how drastic an update it was going to be based on their earnings report : if Yahoo! had a good quarter then the impact on search engine rankings as a result of the index shift was greater.

These days, however, Yahoo! only seems to have one or two major shakeups per year, with a series of smaller ones throughout the year.

Google – Google, of course, is the engine most people watch.

And while Google too has moved to a perpetually updating index, much like MSN, they do have major updates when algorithms are tweaked.

In fact, we have just completed one such update. And as with previous major updates, I was expecting this one.

There were similar indicators as with MSN And Yahoo! In that there was a subtle shift in the number of back links indexed, but the largest indicator for me was the recent doubling of the index.

You see, back when Yahoo! proclaimed ‘Ours is bigger’ Google retaliated with a massive crawl and index. In almost every case I’ve seen the number of indexed pages roughly doubled.

But since many of the sites in question didn’t actually have that many pages I new an adjustment was coming.

At the end of October, the week before Halloween I noticed that the back link counts for all my clients changed significantly. To me this was the beginning of the update, yet no formal announcement from the “traditional” sources happened until a few days later. That’s when Webmasterworld began calling it Jagger. It was still a few days after that that Matt Cutts acknowledged the update on his blog.

And this isn’t the first time I’ve noticed updates before official announcements, this is about the third Google ‘major’ update that has been preceded by either a page or back link count change.

So what does this mean (if anything?)

As you can see, in all three cases there are good indicators preceding an update.

Either you see major changes in links or pages indexed, or even a positive earnings report after which an update happens.

Granted this is by no means scientific. This is just observations I’ve made on a couple dozen client’s websites over the past few quarters.

But when I see the same things happening to these clients at roughly the same time, this to me is an indicator. One which I will be sure to pay attention to in the future.

One final note, I’ve also noticed in Google that updates seem to follow themes. In other words, the update doesn’t happen all over at once. Sure different data centers update at different times, but the update seems to hit different parts of the index at different time.

For example, I don’t see rankings changes on legal sites at the same time as rankings changes on rental sites. They always happen a week or 2 apart.

These changes don’t seem PageRank or authority based but do seem to revolve around the theme or topic of the sites.

Therefore, if you do see changes happening with your site, check your competitors and you may also see changes affecting them. But if you don’t see changes happening with non-related sites, that doesn’t necessarily mean that there isn’t an update, it could just mean that it’s already affected those other sites or hasn’t hit them yet.

Columnist Rob Sullivan is an SEO Specialist and Internet Marketing Consultant at Text Link Brokers

Test Phone Sensors, What They Do, Why They Matter?

Motion Sensors

Accelerometer: The accelerometer can easily be considered as a legacy sensor on smartphones. its use is to determine the orientation of the device(portrait vs landscape) and motion in a 3-D plane. Games you play, usually employ the accelerometer to read montion data.

Pedometer: A pedometer is used to measure the number of steps a user takes while the smartphone is upon their person. An accelerometer, in theory, can be used to fulfill this purppose too; however a pedometer, being built specifically for this purpose is more accurate at measuring footsteps and even does so by using less power.

Environmental Sensors

Fingerprint Sensor: As the name implies, a fingerprint sensor is used to store a user’s fingerprint and, upon a successful match, unlocks the phone. Popularised by the iPhone 5S and now included on the new Nexuses(dubbed ‘Nexus Imprint’), a fingerprint doesn’t actually share a user’s fingerprint with any application; rather, it passes on a ‘Yes’ or ‘No’ value based on a successful match.

Ambient Light Sensor: An ambient light sensor is the unit that is used to measure light in the area surrounding the smartphone. The application, usually, is its use in adaptive or automatic brightness: brighter lighting conditions require a brightly-lit display.

Barometer: Barometers are used to measure pressure. More precisely, barometers are typically used for measuring relative pressure. While barometers can be used to read the pressure in a user’s surroundings, it is usually used for fitness applications where barometers lend their data to measure the number of flights climbed by a user.

Magnetometer: A magnetometer is a sensor that is used to measure a user’s orientation, relative to the four poles. The best example of a magnetometer is in desiging a compass app that tells the user the direction they’re facing and how many degrees off North they are. Another application that commonly uses a magnetometer is Google Maps(during navigation).

Proximity Sensor: To locate your phone’s proximity sensor, all you need to do is look near your phone’s earpiece while being on a call. The proximity sensor’s job is to simply judge whether an object(usually the user’s face) is close to the phone. It works by transmitting an infrared beam that bounces back off a close object and is picked up by a recieving end. The best application of a proximity sensor is switching off the display when a user is on a call.

Heart-rate Monitor: Popularised by the Samsung Galaxy line of phones, a heart-rate monitor measures the user’s heart-rate in beats per minute(bpm). This sensor works by transmitting a high wavelength light into a user’s skin and recieving the waves that bounce back. The rate of blood flow in a person’s capillaries/blood vessels is read to determine the user’s heart-rate.

Humidity/Temprature Sensors: Implicit in the name, a humidity sensor measures the humidity in the vicinity of the user and a temperature sensor does the same for the ambient temperature.

Position Sensors


As we saw, the number of sensors used in a smartphone are aplenty and their uses are only limited by imagination. The good news is, smartphones are only bound to get smarter as more sensors are added to the repertoire with time.

What Does Wyo Mean On Snapchat?

Snapchat has been one of the most popular social media platforms today. It offers you the ability to send timed messages and snaps which helps you stay connected with your friends and family without putting your private data at risk. Snapchat has developed a strong community around the platform that makes uses of short-form videos to produce new content as well.

Not only this, but the platform has also a slew of acronyms for everyday phrases to help make it easier to chat with each other. If you have been using Snapchat for a while then you have probably come across WYO. Let’s take a quick look at it.

Related: How to open a Snap without them knowing in 2023

What does WYO mean?

WYO is an acronym that translates to ‘What you on’. It is a phrase used by people to ask each other about their plans and if they would be up for company during the time. WYO usually is used among friends to discuss plans and is especially coming your way if you are on a vacation or leave from your work.

Where is WYO used

WYO is used in the following scenarios

When you want to ask someone about their plans

When you want to ask someone what are they doing currently

When you want to make plans with someone for the day

When you are catching up with someone, so the subtext of WYO changes to a greeting

If you are aware of acronyms then you might have noticed that WYO is quite similar to WYD and that is true. It is mostly used in the same scenarios as WYD and only differs in the fact that it is mostly used to make new plans rather than catch up with a friend on the text.

Related: Snapchat Emoji Meanings: Here’s what Friendship, Snapstreak, Zodiac and Other Miscellaneous Emojis Mean

How to use WYO

You can use WYO in several ways on Snapchat. Let’s take a look at some of the most common ones.


Snapchat has added new functionality where your face gets superimposed on various animations to make it appear that you are doing outrageous actions. You can use Cameos to send a WYO to your friends. Simply type in WYO in the text field and tap on the ‘Cameo’ icon to your right. Select the cameo that you find appropriate and simply send it to the concerned contact.


Another way to say WYO to your friends is to use stickers. Snapchat has a huge collection of stickers that you can use to accentuate your Snaps. There are dedicated stickers for WYO which means that you can add them to a Snap and send it to your friends. This way you can send them your photo as well as help ask them about their plans.

Related: How to get Insights on Snapchat


The old tried and tested method with nothing fancy and no hoops to jump through. Simply type in WYO for your concerned contact and send over to them to make new plans. If you are feeling a bit fancy then you can add the same WYO text to a Snap and send it to your contact as well. This can come in especially handy if you are already at an event or party that you want to tease your friend.

Related: How To Clear All Conversations On Snapchat

Some other acronyms similar to WYO

Here are some more similar acronyms that will help you spice up your everyday conversations with friends and family on Snapchat.


WYD stands for ‘What’re you doing’ and is a way for people to ask what is up with someone on Snapchat. There are dedicated stickers and cameos for this acronym that should help you make the most out of it on Snapchat.


LMK stands for ‘Let me Know’ and is used to ask for updates or finish of conversations. It usually used in casual deals and classifieds where you would be meeting up with someone for an online listing. LMK is also used to update plans to someone and then ask their opinion on the same.

Related: How To Get Rid Of Snapchat Update


DYK stands for ‘Did you know’ and is a way to share facts with your friends. It can also be used to share gossips or just inform them about new happenings that might be important to them. DYK is a very widely used acronym that is also used by news agencies on Snapchat TV to save space and communicate a news story.


What Does Ion Mean On Snapchat?

In the world of social media, it isn’t enough to just know what different apps do. You also need to understand the lingo for each of those apps. Yes, each of your social media apps has its own lingo including abbreviations, emoticons, etc. In this article, we will cover what the term ‘ion’ means on Snapchat and how you can use it.

What does ‘ion’ stand for?

Simply put, ion stands for ‘In Other News‘. It is an acronym that has come to be used quite universally. Ion’s use extends beyond the confines of Snapchat, and can even be found in text messages and DMs.

Many emoji keyboards have stickers pertaining to ion. You can search for these stickers using the acronym or just ‘in other news’.

Related: Best Snapchat terms and their meanings

How is ‘ion’ used on Snapchat?

The acronym is mainly used to change the topic of a conversation. For example, if you are talking about one thing, but want to shift focus to another, you can use ‘ion’ and then start the next conversation.

It can also be used to start a conversation with someone whom you do not usually talk to. In this regard, ion is used to break the ice and introduce a topic immediately.

Used out of context, ion is a fun way to bring attention to a fact that you would like to share. For example, ‘ion, UFOs are flying around Earth, and no one is really shocked’.

Related: What is Snapchat compass from the latest update

How to use ‘ion’ on Snapchat

You can use the acronym in a myriad of ways on Snapchat. You can use ‘ion’ text in your message, snap, or even in your Snapchat story. BTW, Snapchat also has a sticker for ‘in other news’, that you can add to your snaps.

When used in a snap or story, it is better to create a separate textbox for ion. This lets you highlight the topic rather than the ‘ion’ text. If you don’t feel like typing it out, you could always just use the sticker instead.

Once you have your sticker, you can go ahead and add the fact that you would like to highlight. Tap the background anywhere to add your text.

Send your snap out as you normally would.

Similar terms to ion on Snapchat

Here are some terms that relate closely to ‘ion’. Some of them can even be used interchangeably.

ICYDK: This stands for ‘In Case You Don’t Know’. It can also be used interchangeably with ‘ion’ and ‘FYI’ to signify a change of topic.

News flash: Like ‘ion’, this term can be used to bring attention to a new topic. Usually, something the person cares about.

IMO: This stands for ‘In My Opinion’. IMO is used to voice your own opinion about matters that you hold dear.

FYI: ‘For Your Information’ is quite universally used to inform someone about something they probably do not know.


Some other meanings for ‘ion’ on the web

While used colloquially ion has a very specific meaning, the internet is a vast trove of information. So the use of ion on Snapchat is not as globally accepted as you might think. Here are some other terms that ‘ion’ may refer to.

An atom or molecules that possesses a charge (used primarily in the scientific community)

I Don’t: Ion sounds a lot like the words ‘I Don’t‘ said quickly and casually. This is why it has come to be used as such. For example, ‘ion even know what to say’ (I don’t even know what to say).

Inter Office Note: Used as a way to send messages between people within the same office.


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