No mail for вася2
$ telnet localhost 25
Connected to localhost.
Escape character is '^]'.
220 extsmtp.test.lan ESMTP
250 2.1.0 Ok
250 2.1.5 Ok
354 End data with <CR><LF>.<CR><LF>
From: вася2 <вася2@extsmtp>
250 2.0.0 Ok: queued as EDCA32351B
221 2.0.0 Bye
Connection closed by foreign host.
Heirloom mailx version 12.5 7/5/10. Type ? for help.
"/var/spool/mail/вася2": 1 message 1 new
>N 1 вася2@extsmtp.test Wed Mar 20 10:11 16/555 Тест
From вася2@extsmtp.test.lan Wed Mar 20 10:11:10 2013
From: вася2 <вася2@extsmtp.test.lan>
Date: Wed, 20 Mar 2013 10:10:07 +0200 (EET)
As Carlos suggested, the file tool will tell you if it finds legal UTF-8 byte combinations in a file it otherwise decides as being text (but always remember, file does “only” make intelligent guesses).
The main thing to worry about now is if you laid a bomb somewhere that will go off (unexpected) in the future. When any software using the username is not UTF-8 ready. Difficult to predict. But keep it in mind.
BTW, I wonder if this would be worth a bug report: Can not enter Cyrilic usernames through YaST and or useradd. Simply for finding out what the answer is. The answer could shed light on possible pitfals.
What I miss there is what you changed in /etc/login.defs.
I do not know what exactly you did, but does it allow all Unicode characters (except the few that are not allowed because they will create havoc when used in a username like : and @), or did you only solve it for Cyrilic?
I agree, using unicode in a global newtork is a bad idea (there are chars that look similar but has different codes, like ‘c’ and ‘с’). But I was only looking for a solution for inside-company only. And I’m happy that my favorite Linux does offer the choice to me!