Admins Accuse Microsoft of Hotmail Cap

kurmudgeon writes "The Register is fielding reader tips that Hotmail has placed Draconian limits on the number of Hotmail recipients who can receive an email. The first 10 Hotmail addresses included in a mass email go through just fine, according to these reports. But any additional addresses are returned to sender with a message that reads: "552 Too many recipients." (Microsoft denies it has placed any such restriction on the number of senders.) This would appear to be a violation of RFC 2821, which states: "Rejection of messages (for excessive recipients) with fewer than 100 RCPT commands is a violation of this specification."

Comments

And the problem is...?

[Kelson]

Let's look at that phrasing: "Rejection of messages (for excessive recipients) with fewer than 100 RCPT commands is a violation of this specification." (emphasis added).

Are they rejecting messages, or are they rejecting recipients?

According to this, they're rejecting recipients with an obvious "try this again" code. Really that should be 452, not 552, but that same RFC 2821 says that senders should treat a 552 as temporary:

RFC 821 [30] incorrectly listed the error where an SMTP server exhausts its implementation limit on the number of RCPT commands ("too many recipients") as having reply code 552. The correct reply code for this condition is 452. Clients SHOULD treat a 552 code in this case as a temporary, rather than permanent

So whatever sending server runs into these limits should retransmit the message to the remaining recipients on the next queue run. Okay, it'll only reach 10 recipients at a time, which is annoying. It shouldn't be kicking back the error to the client.

Really, assuming Microsoft has actually put this limit in place, the only thing I can see that's wrong, from a practical standpoint, is using the outdated 552 code instead of the more specific 452 -- but that same RFC people are waving around says that their servers should treat it as temporary anyway.

Am I missing something?