Feeds

Admins accuse Microsoft of Draconian Hotmail cap

'Only 10 recipients at a time, please'

Securing Web Applications Made Simple and Scalable

Life can be tough when you're one of the globe's biggest email providers. Just ask Hotmail. Users get upset enough when come-ons for Viagra slip through the cracks of the Microsoft-owned service. But there's just as much hell to pay when its war on spam snuffs out legitimate emails.

In May, we reported on a proprietary Microsoft technology dubbed SmartScreen, which secretly blocked Hotmail-destined email from entire domains - even when they were a year or more old and were correctly listed in the DNS and had solid SPF records.

Now we're 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.)

That's causing considerable trouble for people like William Old, a UK-based IT administrator who maintains an email newsletter for retired police officers. After sending the most recent newsletter about two weeks ago, he quickly received the 552 notice informing him that 29 of the 39 Hotmail addressees were being returned.

"The issue for us is it's a blow to a well established mechanism for getting an update out to our 550 members," Old says. "It was working perfectly well up until the last month."

Old has since sent several batches of test emails, and each time, exactly 10 are delivered to addresses ending in hotmail.com or msn.com and the rest are rejected with the same 552 failure notice.

It took Microsoft's rapid response team more than 19 hours to provide a three-sentence response to our request for comment. It read:

Microsoft is committed to helping protect email as an essential communications tool and to help protect users worldwide from spam and other e-mail safety concerns. One of the methods we employ to prevent spammers from abusing Windows Live Hotmail is to establish a sending limitation of 250 recipients per day. We do not currently limit the number of recipients per message, however we may consider doing so in the future for new accounts, as additional means to prevent spammers from abusing Microsoft services.

Microsoft's denial doesn't square with recent online discussions in which users report a new spate of 552 failure notices being sent by Hotmail. The initiator of this discussion, for instance, reported that six of 16 messages sent to Hotmail users bounced and said the rejection was a new phenomenon. Other discussions like the one here also appear to report the same cock up.

Microsoft denied our request for an interview with a Hotmail official.

Several people have reported a work-around, which can be achieved by setting the max_rcpt of the SMTP transport to 10 or less. This method worked for Old, but he said it has the potential to consume significantly more bandwidth, a limitation that is sure to hurt legitimate senders but have much less of an effect on spammers, who don't pay for their internet service.

The last time we spoke with a Hotmail official, we learned that of the 5 billion emails sent to its users each day, about 4.5 billion of them, or a whopping 90 percent, were spam. Clearly, unsolicited email is a problem that warrants a tough response from Microsoft.

But the sudden reports of 552 rejection notices are a reminder that brute-force solutions are just as likely to trip up legitimate senders as they are in shielding their users from spam. In this case, it would also appear to violate RFC 2821, which states: "Rejection of messages (for excessive recipients) with fewer than 100 RCPT commands is a violation of this specification."

So the next time you send email to a Hotmail user, give a moment of silence for the beleaguered security pros at Microsoft whose collective finger are all that's blocking a torrent of spam and other crud from spilling over the proverbial dike.

Then say a little prayer that the people you're trying to reach actually get your message. ®

Mobile application security vulnerability report

More from The Register

next story
LibreSSL RNG bug fix: What's all the forking fuss about, ask devs
Blow to bit-spitter 'tis but a flesh wound, claim team
Manic malware Mayhem spreads through Linux, FreeBSD web servers
And how Google could cripple infection rate in a second
NUDE SNAPS AGENCY: NSA bods love 'showing off your saucy selfies'
Swapping other people's sexts is a fringe benefit, says Snowden
Own a Cisco modem or wireless gateway? It might be owned by someone else, too
Remote code exec in HTTP server hands kit to bad guys
British data cops: We need greater powers and more money
You want data butt kicking, we need bigger boots - ICO
Crooks fling banking Trojan at Japanese smut site fans
Wait - they're doing online banking with an unpatched Windows PC?
NIST told to grow a pair and kick NSA to the curb
Lrn2crypto, oversight panel tells US govt's algorithm bods
prev story

Whitepapers

Reducing security risks from open source software
Follow a few strategies and your organization can gain the full benefits of open source and the cloud without compromising the security of your applications.
Consolidation: The Foundation for IT Business Transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.
Application security programs and practises
Follow a few strategies and your organization can gain the full benefits of open source and the cloud without compromising the security of your applications.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.
Consolidation: the foundation for IT and business transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.