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Why does email arrive sooner at one ISP than another?


Some email sent to my Gmail arrives much earlier in my Yahoo mail. By much,
I mean several minutes.

In this excerpt from
Answercast #63
, I look at how email travels and the fact that it can easily
have different arrival times in different services.

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Gmail received earlier

Yes, that is totally expected. Minutes is not something you can count on
when it comes to email.

Remember, email is not (and I really do want to stress “not”) a real time
communications method. It sometimes seems like it is in that sometimes we will
send an email to somebody and they will get it in seconds, but that is in no
way guaranteed. In fact, the entire email infrastructure is designed to
tolerate delays not in minutes or hours, but delays of days. It is very
possible (though relatively unusual these days) for an email to take multiple
days to get from one point to another.

Differences are expected

So I would definitely not see what you’re experiencing as a problem in any
way. It is the normal way that systems work.

In this case, potentially some of the servers were busy and they just didn’t
get around to handling the email that quickly. Perhaps the email that went one
path went through fewer servers than the other one. There are just so many
different reasons that this kind of thing can happen that it’s just not
unusual. It happens all the time and it’s not something that I would build any
expectation around.

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3 comments on “Why does email arrive sooner at one ISP than another?”

  1. So what do I do if I need to send a message and attached file immediately — say the final drafts of a contract being negotiated on a tight deadline?

  2. I thought I read somewhere that all internet traffic is given a priority and email has one of the lowest priorities where as web and VOIP has a higher priority as it’s important to get all the voice bits to the destination at about the same time.

    If you remember the post office, when email was developed it would take the post office several days mail to get from one person to another, so a delay of even one day because there were more important internet traffic, would not be a big deal. One or two days by email was still better than two or three days by the post office.

    We’ve become an instant generation. We expect to get information in an instant. We expect email in an instant. We should be able to heat up our dinner in an instant. We should be able to receive a phone call instantly (not wait to check the machine at home and return a phone call).


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