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Exchange 2010 Receive Connector timming out

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  • Exchange 2010 Receive Connector timming out


    I'm posting this because it's already driving me mad!

    Recently i've installed an Exchange 2010 server with both mailbox+hub transport roles on an VMWare Hypervisor. This was installed in order to migrate from a physicall Exchange 2007.

    Everything is working fine but for the relay connector i've created on 2010.

    There's a process on our SQL Server that uses Database Mail to deliver announcements to about 600 users (i know it's not the way, but tell that to our developers ). This was working on the Exchange 2007 relay connector, but wasnt on the 2010. On the SQL's database mail side there are a lot of timeout errrors:

    The mail could not be sent to the recipients because of the mail server failure. 
    (Sending Mail using Account 2 (2011-10-27T09:47:52). 
    Exception Message: Cannot send mails to mail server. 
    (The operation has timed out.). )
    Both servers are on the same lan segment.

    I was able to reproduce this situation by sending all 600 emails to my account, and it went away when i configured the following properties on the connector:

    MaxInboundConnection                    : 5000
    MaxInboundConnectionPerSource           : 5000
    MaxInboundConnectionPercentagePerSource : 50
    TarpitInterval                          : 00:00:00
    Then i was able to send all 600 emails to my account... i believed this was solved.

    But no... Today i had the same situacion, there were a lot less errors though.

    Can anyone point me in the right direction? thanks!

  • #2
    Re: Exchange 2010 Receive Connector timming out

    (Note: updating my own post just in case someone else has this problem).

    The culprit was the MaxAcknowledgementDelay property. From what i understood, in the SMTP session, at the end of the DATA command, Exchange 2010 waited up to MaxAcknowledgementDelay seconds until the mail was delivered to the remote host. Ie:

    220 Microsoft ESMTP MAIL Service ready at Fri, 28 Oct 2011 09:41:03 -0300
    250 Hello []
    MAIL FROM: <[email protected]>
    250 2.1.0 Sender OK
    RCPT TO: <[email protected]>
    250 2.1.5 Recipient OK
    354 Start mail input; end with <CRLF>.<CRLF>
    From: Maximiliano Kolus <[email protected]>
    To: Maximiliano Kolus <[email protected]>
    Subject: MaxAcknowledgementDelay test
    Damn you MaxAcknowledgementDelay!
    250 2.6.0 <[email protected]> [InternalId=110563] Queued mail for delivery
    221 2.0.0 Service closing transmission channel
    In the (delay) part, there was a short delay where Exchange 2010 was delivering the mail to the remote host, when i got the 250 response it was because the mail was already delivered. If the mail wasn't delivered in MaxAcknowledgementDelay seconds, Exchange will sent the 250 anyway.

    By setting this parameter to 0, the acknowledgement will be sent right away, and my timeout problem was gone.