Finnish language has many many endings, but I cannot search easily the base word, etc by
For instance, searching
Jämsä will not give
Jämsän in the basic Thunderbird search.
A basic regex search would help here.
A differential solution is to use Evolution where the basic search
Jämsä returns messages with contents/title
Jämsän, but one shortcoming is no offline use with IMAP as described in the thread How to setup Evolution IMAP for Offline use?
OS: Debian 9.1
Thunderbird version: default