[derefr]

> Is there any valid reason for this?

If they know that at some point they'll have to ask you to enter your password over a restricted input-method (e.g. on a DTMF keypad.)

[Molomby]

Real world example of this "limited input" problem: http://apple.stackexchange.com/questions/202143/i-included-e...

Pre-Touch Bar, of course...

[colanderman]

Yep. FastMail restricts spaces in passwords due to mail clients that do not allow them.

[nmjenkins]

(FastMail developer here)

The issue was actually that we support many different protocols (not just mail) and some combinations of clients/protocols have had issues in the past (it might have been some FTP clients I think, but can't remember right now.)

Anyway, this restriction no longer applies as we now require server-generated app passwords for 3rd party apps: https://www.fastmail.com/help/clients/apppassword.html. So feel free to use as many spaces as you like in your password!

[colanderman]

I didn't know that, thanks, and thanks for providing a product I can rely on!

[kibwen]

Which clients specifically?