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I'm system administrator in online store. We send several emails to our clients after purchase: confirmation, invoice and sale notification to our staff.

Recently we got most of emails bounced back and some bounces describes a reason as greylisting, others - just general failure.

It is ruining our business because clients are calling that they didn't get the emails with confirmation and invoices.

How to get off greylisting, and to not be greylisted? What actions should we do? Mailserver is dedicated machine using Mailenable on Win 2003.


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up vote 5 down vote accepted

you cannot really get off the greylist. it's mechanism deferring mail delivery. as long as you use reasonable smtp server it will re-try in 10-30 minutes and then grey-list protected server should accept your message.

more info about mechanism here and here.

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Greylisting should return 4XX codes, i.e. "Temporarily rejected". Your SMTP server should not bounce back. If that's the case check your mail server configuration.

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In any case (graylisted or blacklisted) you should contact the postmaster at the intended recipient domain and request that they stop graylisting or blacklisting your domain\server.

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Your email software is not attempting a re-delivery. This is the heart of the greylist mechanism, and is critical to getting through a greylister. There are two possible causes:

  1. The greylister is returning a 5xx code (permanent failure) instead of a 4xx code (temporary failure), causing you to not re-attempt delivery. This means the site you are sending to is broken, and therefore, it is a problem at that location. You'll have to talk to the postmaster for the site and find out what the issue is.

  2. If you are not re-attempting delivery on a returned message with 4xx, your server configuration is, quite frankly, screwed up. You should never immediately fail a 4xx delivery attempt. There's a reason for multiple delivery attempts and 4xx codes: they are there to eventually get your message delivered, even when you can't do it right now.

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