Install claws-mail-archiver-plugin by entering the following commands in the terminal:
sudo apt update sudo apt install claws-mail-archiver-plugin
Archiver plugin for Claws Mail
This plugin for Claws Mail allows archiving of account's folders (IMAP, POP or local) as well as vcalendar folders. . Several formats are supported (TAR, PAX, SHAR and CPIO) with optional compression methods (GZIP, BZIP2).