I notice there is a space after the = in the default setting: #auth_username_chars = abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890.-_@ Is that space part of the syntax or required? If not, does that mean 'space' is included in the default list of allowed characters?

If not, then is the space after the '=' required? -- If not, the implication would seem to be that space is 'ignored'. If that's the case, how does one include 'space' in the list of allowed characters? Also, how does one include the "\" character in the list of allowed characters?

I.e. is anything accepted, literally, after the first non-space char after the '=' sign? I.e. any spaces after the first non-space char would be taken as valid character, and '\' would also be a literal character?

(not that'd I'd be using windows's clients or anything that would, on occasion, pass "DOMAINAME\user" as the calling user trying to log into a 'user' account....or anything....*ahem*...)

Overrode it w/some hard-coded hacks, but would like dovecot to me more robust and handle weird input and do the right thing with it (I know that's always a challenging concept for some people, since the answers and ability to arrive at 'correct' is always 'contextual', and so many people want absolute rules that apply all the time in all cases, but...I think thats a diagnosable psychological condition ;-) ).