In the recent draft, I don't see anything one way or the other about dealing with ambiguities in the existing RFC. While we certainly wouldn't want to change the protocol, it looks to me like there are a few places where we could clarify the language and, if need be, noting implementations have interpreted the language other ways. In Section 3.1, a server can offer two greetings to a new connection, 220 or 554. The semantics of the 554 are utterly unclear. Plausible interpretations include: a) This domain has rejected your mail, give up and report the message(s) as undeliverable, as though you got the 554 in response to DATA. 554 YOU ARE BLACKLISTED. FOAD. b) This server is broken, try others as though you couldn't connect to this one. 554 MY NETAPP IS EMITTING SMOKE. SORRY. c) This server is sort of broken, try others at the same MX priority but not lower. 554 MY SPOOL DISK IS CURRENTLY FULL. SORRY. I don't feel strongly about which is the right interpretation, but it would be nice to know how to code my mail clients. R's, John
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