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Greylisting

 
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chrisf



Joined: 07 Dec 2005
Posts: 16

PostPosted: Sun Apr 23, 2006 12:22 pm    Post subject: Greylisting Reply with quote

In previous posts, I described some problems I was having in sending email to some mail servers. After speaking to a few people I have learnt that this is due to the use of 'greylisting' on the remote server.

I found a good explanation of grey listing, which may explain what I mean more clearly:

"Greylisting is a technique designed to stop spam before it arrives in your inbox. It's implemented on the mail server that initially receives your mail, and works by delaying mail from senders that the mail server has not encountered before.

Delaying the mail works because the SMTP protocol that is used to send all Internet email has a mechanism for handling mail servers that are overloaded or unable to process mail. Greylisting fakes the overload situation, when an email arrives from a previously unseen sender, causing the message to be delayed.

If the sender is legitimate then their mail server will try again (typically within 4 hours). Spammers and email viruses tend to be flybynight operations when sending mail and will not check to see if the mail got through and will not resend undelivered messages.

By implementing greylisting on a mail server most spam and virus email is automatically eliminated. Naturally, there are problems that make greylisting a less than perfect solution, but it's a viable way of eliminating spam and viruses if you control your personal or organization's incoming mail server."
Courtesy of jgc.org

This is what seems to be causing the mail to enter the 'badmail' folder after the remote host delays the mail.

After 2.3.4, you implemented a new timeout feature where it's possible to set the time that the server waits for a response from the remote mail server. Unfortunately, this does not solve the problem, as a response is actually sent from the remote server - basically saying 'busy - try again later'.

Is there any chance the mail server could be set to retry the mail, rather than throw it into the 'badmail' folder?


Last edited by chrisf on Tue Mar 04, 2008 6:22 pm; edited 1 time in total
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admin
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Joined: 13 Apr 2005
Posts: 1470

PostPosted: Sun Apr 23, 2006 1:54 pm    Post subject: Reply with quote

I will see if I can implement this behaviour (retry after x minutes) in a futurte release. But I hope you agree the whole concept is pretty vague...
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chrisf



Joined: 07 Dec 2005
Posts: 16

PostPosted: Sun Apr 23, 2006 5:15 pm    Post subject: Reply with quote

Yeah, I agree it's not brilliant. I wouldn't want to use greylisting myself, however some people obviously do, and at the moment I have to resend email messages manually.

Last edited by chrisf on Tue Mar 04, 2008 6:17 pm; edited 1 time in total
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rnichols



Joined: 13 Apr 2007
Posts: 1
Location: Long Island, New York, USA

PostPosted: Fri Apr 13, 2007 7:25 pm    Post subject: Reply with quote

Pablo,

First and foremost, the software is fantastic. Every other mail server I looked at, you needed a computer science degree to make it work. I set yours up in 10 minutes and it worked right away. Thanks.

Second, any more word on Greylisting and retries? Greylisting has gotten very popular these days.

Thanks,
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Rob
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admin
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Joined: 13 Apr 2005
Posts: 1470

PostPosted: Fri Apr 13, 2007 7:30 pm    Post subject: Reply with quote

I found this very hard to test. All my test account do not have this behaviour, so I can't reproduce it.
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