[HUB] Mail delivery fails on Plesk for Linux: 451 4.7.1 Service unavailable

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    Fran Le Bouleix

    Since April 30, I'm experiencing a similar error on a few Plesk Onyx servers deferring mail for a few domains.
    We have a spam filter before those, so Plesk spam and virus filters are disabled, no greylisting either.

    Plesk:
    - Version 17.8.11 Update #52, last updated on April 30, 2019 on CentOS Linux 7.6.1810 (Core)
    - Version 17.0.17 Update #68, last updated on April 30, 2019 on CentOS Linux 7.6.1810 (Core)
    - Version 17.5.3 Update #71, last updated on April 12, 2019 on CentOS 6.10 (Final)

    I followed debugging steps in this article, everything checks out OK.

    So far the only way I found to get mail going for those domains is to

    1- Switch OFF SPF spam protection in the Mail server settings (which  was set to SPF checking mode = Only create received SPF headers, never block).

    2- Restart Mail service:
    /usr/local/psa/admin/sbin/mailmng --stop-service
    /usr/local/psa/admin/sbin/mailmng --start-service

    /var/log/maillog does not show any warning about any spf problem though, and the originating IP is within the domain  SPF record.

    Just this (Scrubbed for privacy):
    postfix/cleanup[16539]: warning: milter inet:127.0.0.1:12768: can't read SMFIC_BODYEOB reply packet header: Connection timed out
    postfix/cleanup[16539]: 9A42A64010C: milter-reject: END-OF-MESSAGE from XX.XX.XX.XX 4.7.1 Service unavailable - try again later; from=<sender@domain>

    Any thoughts?

    Fran

     

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    Daria Gavrilova

    Hello @Fran Le Bouleix,

    In case if Kaspersky antivirus is used on the server, then the most probable cause of such behavior is that Kaspersky hung.
    More information about this issue you can also find in the following article: Unable to send or receive email: 451 4.7.1 Service unavailable - try again later

    Also the cause of the issue might be that Dovecot and pc-remote services are hung or Milter crashed.
    In this case to resolve the issue following commands should be executed:

    # service dovecot restart
    # service pc-remote restart

    If above actions do not help, please create a request to the Support team: How to submit a request to Plesk support?

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    Fran Le Bouleix

    Unfortunately, Kaspersky antivirus is NOT used, nor is greylisting.

    /Fran

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    Daria Gavrilova

    Hello @Fran Le Bouleix

    The issue requires the deeper investigation on the server directly.
    So it is recommend to contact your Server-Hosting provider if it is not possible to create the support request to Plesk directly.

    If you would like to get the direct support assistance from Plesk, you may purchase the support subscription and then create the support request.

    Thank you for understanding.

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