I had this annoyance with FastMail[0], recently. They give this justification for their restriction: FastMail provides a lot of different services over man

I had this annoyance with FastMail[0], recently. They give this justification for their restriction: FastMail provides a lot of different services over many different protocols. To ensure that your password is compatible with all of them, and the many (often slightly buggy) clients out there, we only allow the characters A-Z, a-z, 0-9 and !?@#$%^&*()-=_+[]{}.,:;<>/\|~"'`. Which I understand, but how about a checkbox that says "for goodness sake, I'm a grown up, I promise not to moan if I use a "buggy" client, now please let me the password of my choosing." [0] https://www.fastmail.fm/help/account/password.html https://www.fastmail.fm/help/account/password.html