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

Symptoms

• Plesk Obsidian running on a Linux-based operating system
• All mail messages migrated from a source server are shown as corrupted on Webmail (Invalid Address and No subject).
• An error that is similar to the following can be seen in the /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:

• A check for one of the files in the error message reveals that it is compressed:

  # file /var/qmail/mailnames/example.com/username/Maildir/cur/1514911697.M278455P5627.cp.example.com,S=12483,W=12780:2,S /var/qmail/mailnames/example.com/username/Maildir/cur/1514911697.M278455P5627.cp.example.com,S=12483,W=12780:2,S: gzip compressed data, from Unix, original size modulo 2^32 12483

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

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

Cause

The Plesk Migrator transfers messages as they are, meaning without any modifications. Since the messages are compressed on the source server, after the migration, the destination Plesk server is not able to work with them.

This behavior is recorded as a Plesk Migrator extension bug with ID #PMT-4651, which will be resolved in future updated for the Plesk Migrator.

Resolution