Symptoms
When transferring an account from a DirectAdmin server, messages do not appear when viewing a transferred mailbox. The files appear on disk but not in Webmail or any other mail client.
Dovecot fails to open message files with errors:
Sep 14 16:42:24 srvr dovecot: imap(user@example.com)<3658762><id>: Disconnected: FETCH failed: Mailbox INBOX.Drafts: UID=23346: zlib plugin: Detected .zstd compression but support not compiled in in=491, out=3534, bytes=491/3534
Sep 14 16:42:26 srvr dovecot: imap(user@example.com)<3658793><id>: Error: Mailbox INBOX.Drafts: UID=23346: zlib plugin: Detected .zstd compression but support not compiled in
Sep 14 16:42:26 srvr dovecot: imap(user@example.com)<3658793><id>: Disconnected: FETCH failed: Mailbox INBOX.Drafts: UID=23346: zlib plugin: Detected .zstd compression but support not compiled in in=676, out=4874, bytes=676/4874
Description
DirectAdmin has optional support for zstd compression in Dovecot. cPanel does not currently support this compression method, so it cannot open these message files.
Workarounds
In future transfers, ensure zstd compression is disabled on the source server. We recommend disabling compression on the origin server, removing the account from cPanel, then transferring the account again.
Enabling email compression for existing emails | DirectAdmin Docs
If this is not possible, a system administrator can use the zstd utility to decompress the transferred message files manually.