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In Wikipedia it sais:

A mail transfer agent (MTA) using greylisting will "temporarily reject" any email from a sender it does not recognize. If the mail is legitimate the originating server will, after a delay, try again and, if sufficient time has elapsed, the email will be accepted.

But how can I find out how long these delays are on my server and on the receiving side?

My goal is to speed up email-traffic with partners using greylisting too and speed up the receiving of the first email someone sends to customers on my server.

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closed as off-topic by Rex, Ward, MadHatter, Jenny D, ceejayoz Oct 29 '13 at 15:42

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4  
The delay on the sending side would be determined by the retry interval configured in the MTA settings. I have no idea what it would be on the receiving side, but I suspect it's configurable and therefore variable, based on the particular configuration of each receiving server. –  joeqwerty Sep 7 '13 at 20:07

3 Answers 3

up vote 1 down vote accepted

I assume you're the sending party since you've then mentioned the receiving party.

The delays on the sending party's side (you) is entirely dependant on the software being used (you haven't mentioned). In Postfix, there are various configuration parameters to control this, the default retry timeout being 300sec (5 minutes) in current versions.

As for the delays on the receiving side (the ones enforcing grey-listing), there is no technical method to determine their configuration. You either need to reach out to the admin and ask politely, or do a series of trial-and-error tests. If I were the remote admin, I'd much prefer you ask me first.

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So any objections if I set the queue_run_delay value to 100? –  rubo77 Oct 28 '13 at 22:56
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Without being rude, I couldn't care less what your queue_run_delay is set to; it makes no difference to "me" as a receiving mail server. You haven't stated what your goal is, so I can't offer any input on the consequences of changing this, or if it will achieve your goal(s). –  fukawi2 Oct 29 '13 at 2:03
    
OK, as I understand, setting that queue_run_delay down will only speed up mails from customers sending from my server to receipients on servers that have greylisting and have a delay smaller than 100 too. When sending to my servers, that still have the default 300 I cannot optimize anything from my side. But I can speed up the --delay parameter rleir mentioned ;) –  rubo77 Oct 29 '13 at 13:43
    
Yes, you can reduce your timeout on messages being sent to you, but there is no way to control how long the sender will wait before retrying (probably the biggest shortcoming of grey listing) –  fukawi2 Oct 29 '13 at 22:30

It's entirely dependent on the software being used to perform the greylisting and almost all of them will have a method to customize this value.

edit after your edit to the question:
Speeding up email traffic to partners using greylisting would involve getting your partners to exclude your emails so they are not delayed by the greylisting process.

Speeding up receving emails someone sends to your server will be hit or miss because different sending MTA's will retry at different intervals. If their first email is greylisted, the sending MTA might try to resend the message after 5 minutes, or 30 minutes, or sometimes never (it depends on how they have their server configured). You can "speed it up" by not using greylisting or whitelisting specific sender domains on your end to not deny the initial message.

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In postgrey when receiving email the default is 300 seconds. That is, if the sender retries within 300 seconds it will be rejected again. Change that to, say, 60 seconds in /etc/default/postgrey with

--delay=60

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