I have been having a problem with a major high speed ISP in that some of their emails inbound are being blocked by my firewall - in accordance with RFC 821, (SMTP), because they are sending line lengths in the data portion of the transaction that exceeds 1,000 characters without a CR/LF. Testing proved that they were exceeding 2,000 characters and I gave up at that point.

The ISP in question does not handle it's own email system.... .... so we had a conference call and I was told that it wasn't their problem.... Then we reproduced the issue for them that showed that some of their servers are compliant and some aren't. Then I found further evidence that the ISP in question was causing issues for others with my make/model of firewall for the same reason and it all started in July which is about when our issues were brought to my attention.

So, today I heard - _off_ the record - that this ISP does no enforce RFC 821 but, rather, they use RFC 822 as their standard. So I take a quick look:-

RFC 822 is the RFC for the "Standard for ARPA Internet Text Messages" and supercedes RFC 733. I cut to the quick and looked in the syntax section and there are none of the basic SMTP commands included, (HELO, RCPT TO, etc.). There are some equivalent commands for some of the data fields but that's somewhat academic. Furthermore, there is no reference to the 1,000 character limit without a CR/LF or any other reference to a "line break" etc.

Now, (and I'm already pretty sure of the answer but I'd like someone else's opinion who has some understanding of this and the relation to the various RFC's), I understand that SMTP is a text based protocol... BUT.... can anyone sensibly impose RFC 822's rules over and above the rules laid down in RFC 821 or am I being bullshitted by a major company, (the email provider not the ISP), in the hope I will shut up......

[EDIT]

Ok, I found RFC 2821... But I quote from it:-

This document is a self-contained specification of the basic protocol
for the Internet electronic mail transport. It consolidates, updates
and clarifies, but doesn't add new or change existing functionality
of the following:

- the original SMTP (Simple Mail Transfer Protocol) specification of
RFC 821 [30],

So.... They can't use that one either....

[/EDIT]

Thoughts?