Migrated mail messages from cPanel are showing as Invalid Address/No subject in Plesk server: Corrupted record in index cache file

Symptoms

• All mail messages migrated from a source cPanel server are shown as corrupted on Webmail(Invalid Address and No subject). The following error is seen on /var/log/maillog:

  CONFIG_TEXT: dovecot Error: service=imap, user=username@example.com, ip=[127.0.0.1]. Mailbox INBOX: UID=33261: read(/var/qmail/mailnames/example.com/username/Maildir/cur/1520269963.M402118P28216V0000000000000802I00000000001840FA.CL0016UC-SG1.WEBVIS.NET,S=1448:2,S) failed: Cached message size larger than expected (1448 > 1188, box=INBOX, UID=33261)
  dovecot: Error: service=imap, user=username@example.com, ip=[127.0.0.1]. Corrupted record in index cache file /var/qmail/mailnames/example.com/username/Maildir/dovecot.index.cache: UID 33261: Broken physical size in mailbox INBOX:

• On the source cPanel server, dovecot has compression enabled:

  # cat /etc/dovecot/dovecot.conf | grep zlib
  zlib_save_level = 6

Cause

Plesk migrator transfers messages from cPanel "as-it-is" without any modifications, so the messages are compressed after the migration and Plesk is not able to work with them. This Plesk Migrator extension bug with ID #PMT-4651 which plans to be fixed in future extension updates.

Resolution