restricted, unrestricted) Some mail systems have great difficulty dealing with the full spectrum of addresses allowed by RFC 822. A particularly common example of this is sendmail-based mailers with incorrect configuration files. Quoted local-parts (or mailbox specifications) are a frequent source of trouble:
"freed, ned"@ymir.claremont.eduThis is such a major source of difficulty that a methodology was laid out in RFC 1137 to work around the problem. The basic approach is to remove quoting from the address and then apply a translation that maps the characters requiring quoting into characters allowed in an atom (see RFC 822 for a definition of an atom as it is used here). For example, the preceeding address would become:
freed#m#_ned@ymir.claremont.edu
The restricted channel keyword tells PMDF that the channel
connects to mail systems that require this encoding. PMDF then encodes
quoted local-parts in both header and envelope addresses as messages
are written to the channel. Incoming addresses on the channel are
decoded automatically.
The unrestricted keyword tells PMDF not to perform RFC
1137 encoding and decoding. unrestricted is the default.
Note:
Therestrictedkeyword should be applied to the channel that connects to systems unable to accept quoted local-parts. It should not be applied to the channels that actually generate the quoted local-parts! (It is assumed that a channel capable of generating such an address is also capable of handling such an address.)