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:

Cause

On the source cPanel server, dovecot has compression enabled:

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

Plesk migrator transfers messages from cPanel "as-it-is" without any modifications, so the messages are compressed on the source server. 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