Install sylph-searcher by entering the following commands in the terminal:
sudo apt update sudo apt install sylph-searcher
Description:
Full-text search program for Sylpheed or MH folders
Sylph-Searcher is a Full-text search program for messages stored in the mailboxes of Sylpheed, or generic MH folders.
Homepage: https://sylpheed.sraoss.jp/
Version: 1.2.0-13
Section: universe/mail