[FIXED BUG] Plesk email account via Outlook IMAP/POP3 returns the following after syncing: Message appears to be a Unicode message and your E-mail reader did not enable Unicode support.

Symptoms

• Plesk Obsidian is used:

  # plesk -v | grep 'Product version'
  Product version: Plesk Obsidian 18.0.25.0

• After connecting Plesk mail account to Outlook, it returns any of the following error messages after syncing:

  CONFIG_TEXT: Message 2536 appears to be a Unicode message and your E-mail reader did not enable Unicode support. Please, use an E-mail reader that supports IMAP with UTF-8(see https://tools.ietf.org/html/rfc6855.html)

  CONFIG_TEXT: This E-mail message was determined to be Unicode-formatted but your E-mail reader does not support Unicode E-mail. Please use an E-mail reader that supports POP3 with UTF-8 (see https://tools.ietf.org/html/rfc6856.html)

• Courier-IMAP was upgraded to version 5.0.

  # rpm -qa | grep courier-imap
  psa-courier-imap-5.0.8-2.centos.7+p18.0.20.2+t191101.1317.x86_64

• The issue may appear in other mail clients also

Cause

Courier-IMAP 5.0 implements rfc6855 and rfc6856, which result with an alert in any IMAP/POP3 client on attempt to fetch a mail message with national symbols (UTF-8) in headers. This happens because mail client does not implement properly changes made in rfc6855 and rfc6856.

Resolution

Workaround

If update is not possible for some reason you may try the following