Archiving e-mails by using MailMate as the client and not Apple Mail

Hi!
I use MailMate as my preferred client e-mail and not Apple Mail.
I want to archive some old e-mails in DT so that I can search for them when I need to.
I know I can set up a database and insert e-mails via drag-and-drop e-mails, but I don’t think they will be synced later or progressively.
Thus, I should manually update the database.
Am I wrong?
Is there any other possible solution?

MailMate’s script support is very limited and not sufficient to automate archiving/importing, therefore there’s probably no better solution.