E-mails are not delivered through email clients like Thunderbird and Outlook

Created:

2016-11-16 13:08:11 UTC

Modified:

2017-08-08 13:28:32 UTC

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E-mails are not delivered through email clients like Thunderbird and Outlook

Applicable to:

  • Plesk 12.0 for Linux

Symptoms

Emails are not delivered through email clients like Thunderbird and Outlook with SSL/TLS . Can't send/receive. However webmail works fine.

Cause

Misconfiguration of config file /etc/courier-imap/imapd-ssl . Mail clients are not unable to connect through TLS (latest version).

Resolution

  1. Comment out the following line from /etc/courier-imap/imapd-ssl file to fix the issue:

    #TLS_CIPHER_LIST="HIGH:MEDIUM:!SSLv2:!SSLv3:TLSv1:!LOW:!EXP:!aNULL:!ADH:@STR
  2. Check if the connection works through TLS:

    # openssl s_client -connect  imap.example.com:993 -tls1
    CONNECTED(00000003)
    depth=3 C = SE, O = AddTrust AB, OU = AddTrust External TTP Network, CN = AddTrust External CA Root
    verify return:1
    depth=2 C = GB, ST = Greater Manchester, L = Salford, O = COMODO CA Limited, CN = COMODO RSA Certification Authority
    verify return:1
    depth=1 C = GB, ST = Greater Manchester, L = Salford, O = COMODO CA Limited, CN = COMODO RSA Domain Validation Secure Server CA
    verify return:1
    depth=0 OU = Domain Control Validated, OU = PositiveSSL Wildcard, CN = *.example.com
    verify return:1
    Certificate chain
    0 s:/OU=Domain Control Validated/OU=PositiveSSL Wildcard/CN=*.example.com
    i:/C=GB/ST=Greater Manchester/
    ...
    ...
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