dovecot logs - failed: Invalid quoted-printable input trailer: '=' not followed by two hex digits

Symptoms

Unable to view some emails in Webmail, and /var/log/maillog shows:

CONFIG_TEXT: failed: Invalid quoted-printable input trailer: '=' not followed by two hex digits

Cause

The affected email messages do not fully conform to the MIME Quoted-Printable encoding standards outlined in RFC 2045.

Resolution

You will want to modify the Dovecot template to allow those emails to be visible in Webmail. Steps have been provided below on how to do so.

1. Copy the existing default Dovecot template file by running the following command:

   # cp -ax /var/cpanel/templates/dovecot/main.default /var/cpanel/templates/dovecot/main.local

2. Modify /var/cpanel/templates/dovecot/main.local and edit this section:

   CONFIG_TEXT: [%- IF protocol_imap.imap_capability.defined %]
   imap_capability = [% protocol_imap.imap_capability %]
   [%- ELSE %]
   #imap_capability =
   [%- END %]

   to instead be:

   CONFIG_TEXT: [%- IF protocol_imap.imap_capability.defined %]
   
   imap_capability = "IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE IDLE SORT SORT=DISPLAY THREAD=REFERENCES THREAD=REFS THREAD=ORDEREDSUBJECT MULTIAPPEND URL-PARTIAL CATENATE UNSELECT CHILDREN NAMESPACE UIDPLUS LIST-EXTENDED I18NLEVEL=1 CONDSTORE QRESYNC ESEARCH ESORT SEARCHRES WITHIN CONTEXT=SEARCH LIST-STATUS MOVE"
   # imap_capability = [% protocol_imap.imap_capability %]
   [%- ELSE %]
   #imap_capability =
   [%- END %]

3. Rebuild the Dovecot configuration by running this command:

   # /scripts/builddovecotconf

4. Restart the Dovecot service:

   # /scripts/restartsrv_dovecot