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I asked a question regarding email delays a few months ago, and I think I found a workaround. I changed our email from "" to "", and it seems to work instantly again.

After reading some articles, I believe this could be due to some form of greylisting, though some servers might call it something else -- if a server like yahoo or gmail receive email from a server that it is not used to receiving email from, then sometimes the delay occurs. But a name such as yahoo, gmail, which requires a user to sign up manually -- this delay can be avoided.

My question is this: does anyone know more about this issue -- especially since it would be nice to send an email from our own site, instead of needing to use a whitelisted server?


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migrated from Feb 21 '10 at 10:41

This question came from our site for professional and enthusiast programmers.

would you mind posting a link to that previous question? thanks. – Patrick R Feb 21 '10 at 11:02

While this might be better off on ServerFault; I'd suggest checking what error messages your outgoing emailer (sendmail, postfix, etc?) is generating, if any. Oftentimes those messages will include a response from the remote servers as to why they're declining the email you're attempting to send.

You may need to register your mail server as a valid outgoing mail source on lists like Spamhaus.

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If you have a static IP that doesn't belong to some colo it should just be a matter of contacting whichever mailserver responsible and requesting that they add your IP to their whitelist. Also do a Google search for SMTP whitelists and put your IP address on as many as you can find. I did this right when I started up my SMTP server and within a couple months I was getting mail through without an issue.

Of course all of this assumes you're not sending out some kind of mass email in which case you're probably going to have to jump through some more complicated hoops.

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Very interesting -- will attempt this. – Michael Feb 21 '10 at 9:20

See more information about greylisting on Wikipedia. Typically though, the greylisting interval is five minutes. That is, a retry after five minutes has passed will succeed. The retry won't happen after exactly five minutes though; as you can see in the linked article, the retry interval of mail servers vary, some use ten minutes, others sixteen etc, so a delay of about fifteen minutes can probably be considered normal when greylisting is in action.

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Right; however, I've also read that greylisting can take up to 24 hours (which I've experienced) -- which makes for some terrible UI when someone tries to access my site. – Michael Feb 21 '10 at 9:19
Yes, there are corner cases that take longer. For example, if a site uses an outgoing mail server cluster, where each retry comes from the next server in the cluster, all of their servers will have to get "ungreylisted" before the mail is delivered. But I think that in general it is faster, and also this is a recipient policy. If the recipient decides to use greylisting, they should be aware of the delays this might cause. Popular email hosts like Gmail etc don't. – Jakob Borg Feb 21 '10 at 9:42

You can't get around greylisting, but you can request that users you are sending emails to whitelist you. Just changing the name shouldn't affect greylisting as most depend on on a hash of the sending server ip and recipient. If you could bypass greylisting by just sticking on the end it wouldn't be very effective at blocking spam.

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