I've been wanting to transition off fastmail and google apps mail for a while to mutt but sometimes I get email with attachments and images and I still don't un

I've been wanting to transition off fastmail and google apps mail for a while to mutt but sometimes I get email with attachments and images and I still don't understand what the best practice is to deal with those. I'm on debian buster. I also need to migrate like 50 gigs worth of email. Some of that is in those 2 services and some of that in mail folders on Mac OSX.