[Dovecot] Overloading IMAP Server

Robert Schetterer rs at sys4.de
Tue Jan 22 11:27:03 EET 2013

Am 22.01.2013 10:20, schrieb Robert Schetterer:
> Am 22.01.2013 10:04, schrieb Steffen Kaiser:
>> On Mon, 21 Jan 2013, Harford, Ken wrote:
>>>            I am having an issue with dovecot IMAP reading and writing
>>> to one specific mailbox. I have a check email delivery script that sends
>> What's the purpose of the verification:
>> + The prompt delivery?
>> + The delivery at all?
>> + The correct delivery?
>>> out a email and then logs into dovecot to check if the mailbox that
>>> the message has been delivered to. However, the servers that send
>>> these messages send them in bunches depending on how many postfix
>>> spools it is checking. So I could get 60 messages all being sent to 1
>>> mailbox and then having to read that same mailbox to check if the
>>> message actually got delivered.
>>> I am getting a lot of  errors such as the following:
>>> Could not connect to IMAP server
>>> imap failed: IMAP RECEIVE CRITICAL - Could not select INBOX
>> Is this an error logged by Dovecot?
>>> Any ideas as to what I can tweak in dovecot to allow these messages to
>>> be verified.
>> a)
>> Wait a bit before logging into the IMAP server and check the messages
>> sequentionally, not in parallel. E.g. your script could synchronize
>> itself with other parallel instances by a shared lock.
>> b)
>> Use mail_log and a script on the mail server monitoring Dovecot logs and
>> register delivered message ids and/or recipient. Then figure out a good
>> way to probe, if one pariticular message has been seen.
>> -or-
>> make note of message id/recipient on the sender side, somehow push (ssh
>> or something) that information on regular basis to the mail server,
>> where a script verifies that data.
>> c) To verify the correct delivery: use some sort of checksumming.
>> Kind regards,
>> -- Steffen Kaiser
> Hi , i think you like to do some monitoring ?
> you may do it like this
> if you have i.e xymon client on the mailserver and a central xymon
> monitoring server , write a server mailscript which sends some check
> mail i.e all 5 minutes from the monitoring server to the mailserver
> then on the mailserver write some simple mailcheck monitoring client script
> if the mail arrived i.e in .new of the maildir mailbox i.e all 5 mins ,
> go yellow if it failed for two times, go red if this fails for three times
> simply delete the test mail after check, use a special check mailbox
> which is not accessable from outbound ( postfix access table etc )
> if you want additional imap/pop3 check with the test mail the check
> script could use i.e some imap/pop3 console mail reader perhaps mutt or
> pine etc for reading and deleting the test mail etc, you may integrate
> checksumming at some stage
> i wouldnt deal with logs for this kind of monitoring, or you may
> do it addtional
> i think there are nagios scripts allready ,which might work this way
> Best Regards
> MfG Robert Schetterer

however all monitoring server have simple imap and pop3 checks at default
so the will alarm you when there get no login slot at the mailserver

real time log monitoring is more complex, and mostly event related
which might different from server to server

Best Regards
MfG Robert Schetterer

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