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Thread: Slow SMTP Requests on distributed Zimbra 5.0 Installation

  1. #1
    Join Date
    Nov 2007
    Rep Power

    Default Slow SMTP Requests on distributed Zimbra 5.0 Installation


    We have installed Zimbra 5.0 RC 2 on 4 servers - a distributed installation with the following configurations:

    Server 1 MTA and Mailbox 1
    Server 2 LDAP
    Server 3 Mailbox 2
    Server 4 Mailbox 3

    MTA authenticates against Mailbox 1.

    We have currently the following problem: SMTP requests are most of the time quite slow, so that it takes more that one minute to send an email via the MTA with or without authentication. It seems that after the MAIL FROM: SMTP command the system waits for 20 to 30 seconds and after the RCPT TO: also.

    Has someone experienced similar problems?

    Best regards,


  2. #2
    Join Date
    Oct 2005
    Thatcher, AZ
    Rep Power


    Any indication of a problem in /var/log/zimbra.log

  3. #3
    Join Date
    Nov 2007
    Rep Power

    Default DNS slowing down SMTP processing on multi-server installations

    Dear all,

    The cause for the slowness of the SMTP requests were DNS calls, which were very slow. After the modification of the /etc/hosts file, then the speed of the SMTP requests improved dramatically. Our /etc/hosts/ file now contains the ip address resolution of all 4 servers we are using.

    Another possible solution would be a cached DNS server. But the /etc/hosts file solution is much easier to implement.

    Does not Zimbra, postfix, saslauthd cache DNS requests?

    This is an issue that possibly some customers will be facing.

    Kind regards,


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