I currently use Thunderbird as my email client and it has some filters, but that seems to be all I can program in it.

On several occasions, I heard people talk about their automated email workflow. One example:

When I do not get a reply to an email the script will send a “nag” email asking why I did not get a response yet.

Or another one:

I get so much mail that I cannot read them all. After a week, unread email is put on hold and the sender gets a “if it was important, reply to this email and it will be set to un-hold” email. The script then takes the answer and move it to back into the important folder.

I read about FiltaQuilla which seems nice, but it does not seem to be the kind of programming that I am looking for.

How can I write general purpose scripts like those? Do I need to write my own Python IMAP/SMTP client (if that is even possible) to to this or can I script it it, say JavaScript, in Thunderbird?