Cannot sub address using dotted quad

[Measl]

There is no way to subscribe someone at a dotted quad
IP address. The argument of

     userx@[1.2.3.4]

is rejected as an "illegal" address (although this is in fact
the RFC correct way to do it). Interestingly, I can use

     userx@1.2.3.4 (note lack of brackets)

successfully, but since this is technically not RFC
compliant, many MTAs will refuse to accept it (e.g.,
postfix, and probably others). For example:

220 mx1.mfn.org ESMTP Postfix
ehlo mfn.org
250-mx1.mfn.org
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250 8BITMIME
mail from: <email address hidden>
250 Ok
rcpt to: antisocial@192.168.155.108
501 Bad address syntax
rcpt to: antisocial@[192.168.155.108]
250 Ok
quit
221 Bye

[http://sourceforge.net/tracker/index.php?func=detail&aid=967454&group_id=103&atid=100103]