Helping people with computers... one answer at a time.

Counting on email being almost instant is probably a bad idea. Email is designed to tolerate many delays, and delays do happen.

When someone sends me an email I don't get it right away - sometimes it takes hours. It is time stamped hours before I actually get the message. Could it be because my inbox is too full?

We've all gotten so used to email being an almost instantaneous communications medium that we really notice when there's a delay. The fact is email delivery can be delayed for many reasons, and counting on it to be nearly-instant is just a bad idea.

Couple that with the fact that the timestamps on email often lie, and it can be really difficult to understand exactly what happens when email takes a little too long.

When mail is sent, it may travel across multiple servers. The sender's email server and yours, of course, but it's also possible that several mail servers may also be involved, each one receiving the mail, and then passing it on to the next server along the route. There's actually no requirement that those servers operate quickly, or in any timely fashion. In fact, if they're overloaded with mail, spam or other things, they could simply be slow - and technically that's ok.

In fact, in most cases of delayed email, it's simply due to one of the mail servers along the way being overloaded and running slow - most frequently due to flood of spam. Naturally there are other potential causes for delays, including even how often you check your mail. And delays could be minutes, hours, or in worst case scenarios, even days.

" most cases of delayed email, it's simply due to one of the mail servers along the way being overloaded and running slow - most frequently due to flood of spam..."

A full mailbox is typically not a reason for a delay. For most email services, if your mailbox is full, the message is returned to the sender indicating that it could not be delivered. On rare occasions, it might also simply be discarded. Now, the sender, on getting that notification could try again, and if you'd made room in your mailbox since the first attempt, the mail might be delivered. Depending on how long all that took, it could look like a delay, but it definitely wasn't automatic. The sender had to take steps to re-send the mail.

One thing that can make things very confusing to you as the recipient of email, is that the date and time displayed on the email are, usually, the date and time on the sender's computer. If they have that date and time wrong? Doesn't mater - that's the date and time that shows up on the email. If you've ever seem email (particularly spam) "from the future", that's often what's happened. The clock on the computer sending the email is set wrong.

If you examine the mail headers of a message, you can see the date and time that each mail server along the way acted on the message. The header will have a series of lines that look similar to this:

Received: from (HELO (
  by with SMTP; 13 May 2005 21:33:53 -0000
Received: from mail pickup service by with Microsoft SMTPSVC;
     Fri, 13 May 2005 14:33:53 -0700

It's important to note that each timestamp also includes its time zone designation. In this example "21:33:53 -0000" recorded by the first transaction is UTC or Universal time (less accurately referred to as Greenwich time.) The "14:33:53 -0700" is the same time, but in the Pacific time zone which, at that point, was 7 hours behind UTC.

In theory, once you account for time zones, you can trace relatively accurately how long mail spent on each server along the way, and thus identify any potential bottlenecks.

However, this has one interesting flaw: it still assumes that everyone's clock is set correctly - including all the mail servers. In most cases this is fairly accurate, at least to within a few seconds, but it's definitely not foolproof.

Article C2650 - May 12, 2006 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

Raven Wrting-desk
April 23, 2008 12:19 PM

Hi Leo
I've searched the 'net a bit for this, but haven't found specifics so far.
>> a. How long does e-mail delivery typically take? What are the most common ranges?

>> b. How long does it actually take (more and less) for the mailer-daemon at my e-mail host (or whoever) to find the addressee mailbox is full, the addressee is unknown or otherwise undeliverable? (such as address misspelled)

>> c. Where the addressee data seems valid, how long will the mailer-daemon at my e-mail host (or whoever) keep trying?

I've seen e-mail delivery taking from some seconds (less than about a half minute) to as much as days--but less than a week.
Once in a great while, I've received a message from a "MAILER-DAEMON" saying the daemon is finding some delay, but sending seems okay and the daemon will keep trying for some days; the daemon further explained that I needn't be concerned about it for now. The mail will either be delivered (with no further notice) or at the end I'll get a returned mail with some explanation that the destination seemed okay but wouldn't fully respond.

I found
"generally measured in seconds. It may only take 5 seconds or so"
but no references, no date(s).

Answers to these questions might be of general interest to people frequently replying and to pen pals.

Thank you
R W-d

February 5, 2009 10:05 AM

all of my clocks are set correctly, EXCEPT. yahoo email. I have been thro most of your imformation. ia there a simple way to set that I can understand? i am not a geru.

March 24, 2010 2:02 PM

I met an american couple in Feb 2009 in Venice and I exchanged contact details with them. Shortly afterwards I sent them an email to which I never received a reply until now (March 2010). Without going into too much detail, he replied as if I'd just sent it which I thought was strange and when I queried why he was only now getting in touch he replied the email had just arrived and he'd replied as soon as he'd received it. I want to know how it is possible for an email to take more than a year to reach it's recipient? In the original email I sent I there was a photograph and a link to an online documentary that was quite politically sensitive. Could that have been the reason for the delay? I am in the UK and the recipients live in the USA.
It would be great if you could shed some light on this. Thanks.

December 11, 2010 9:42 PM

I can not read my mail Why?

Please help me to read

March 14, 2011 2:39 PM

I would like to know why it takes so long to get an email from my husband that is in the next room. I don't get them sometimes until the next day.

Basically the article you just commented on has that answer. Just because you're in the next room doesn't mean anything. The email you send still goes to your email provider (wherever they are), then to your husband's email provider (wherever they are) and then finally to your hiusband's computer.

December 15, 2011 6:50 AM

Hi Leo...

well, I've been making this Email since a long time ago, more than three months. but I still never get a notified by the website who's require an email approval for the verification. and I've sent a verification from the web over and over again, but I still haven't got one until now. why is that?
and I've been using another web to register too, and whenever it uses an email approval, the verification still never been sent on my email..

please answer this.. thank you very much..

Hard to say. Make sure that you're typing in your email address EXACTLY correct, and that the verifications aren't ending up in your spam folder.

Update: the email address you provided here was invalid and bounced. That would explain everything. Again, make absolutely certain you're using the correct email address.

January 17, 2012 3:34 PM

it takes me forever (15+ minutes) to get work emails in outlook whereas everyone else (with outlook) gets them in "normal" time.

May 6, 2012 9:05 AM

I have had some issues with delayed emails on AOL recently (after many years without issue.) I first started to notice because my smartphone actually shows the time the email was sent. I've even run tests myself between different email accounts. The delays seem to be sporadic - and AOL haven't been much help. One thing I would like to ascertain though, is whether bulk emails arrive much later. Many of these arrive some hours after the time recorded as 'sent.'

June 22, 2012 12:22 AM

Thank you for this site- it's helped be understand a number of things!!!

Keep up the excellent work!! ;-)

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