From: SM [mailto:sm(_at_)resistor(_dot_)net]
Sent: Saturday, October 29, 2011 1:59 AM
To: Murray S. Kucherawy
Subject: RE: 4yz Temporary Rejections is part of the SMTP Protocol
John suggested a new reply code series, but that scares me a bit;
what would a staunch legacy implementation be likely to do with that?
The legacy implementation could ignore it. In practice, it may cause
code path issues if there isn't any protocol negotiation.
A well-planned specification will presume the latter.