This is going to sound weird, but my father can't send email with attachments currently. I'm a long time fastmail user/customer and I'm also a long time IT guy

This is going to sound weird, but my father can't send email with attachments currently. I'm a long time fastmail user/customer and I'm also a long time IT guy so can't see what's going on. Basically SMTP login and everything works fine, client sends the message and then it just times out.