SMTP syntax errors

[fanf]

Phil Chambers complains about non-ASCII junk in SMTP envelopes:
http://www.exim.org/mail-archives/exim-users/Week-of-Mon-20050718/msg00029.html

I note that another common syntax error is to put a space between : and < and talk about building support into Exim to deal with this misbehaviour:
http://www.exim.org/mail-archives/exim-users/Week-of-Mon-20050725/msg00102.html

More followups discussing ways of configuring existing versions of Exim to do this, and the wiseness thereof:
http://www.exim.org/mail-archives/exim-users/Week-of-Mon-20050725/msg00141.html
http://www.exim.org/mail-archives/exim-users/Week-of-Mon-20050725/msg00147.html
http://www.exim.org/mail-archives/exim-users/Week-of-Mon-20050725/msg00169.html

(I also note that Exim is already strict in this manner about HELO domains.)

[update]
Using $smtp_command_argument to implement :< strictness:
http://www.exim.org/mail-archives/exim-users/Week-of-Mon-20050725/msg00184.html
http://www.exim.org/mail-archives/exim-users/Week-of-Mon-20050725/msg00191.html