WIGHT HAT BLOG

BT \ Yahoo email not suitable for time travellers

Mike Atkinson, May 6, 2011

An interesting problem from one of our customers this week… Suddenly in the middle of the week a large chunk of their outgoing mail was being rejected. With a large publicity drive going on the last thing they needed was to have to deal with hundreds of email bounces a day.

The rejected mails were all being sent to btinternet or yahoo email addresses and all had the failure message ’554 Message not allowed’ in the mail response. When your email bounces it normally gives plenty of information to find the root cause, in this case along with the error message we could also see that the date the original mail was sent was apparently one week in the future!

After a little bit of digging we found that BT & Yahoo now share mail servers, and these servers have strict instructions to reject any mail sent from the future.  What time travelling foe could be so evil as to warrant this email stonewall? Daleks for one are clearly not cut out for work involving typing. It seems that these mails from the future come from a much more resourceful enemy, that anyone with email knows all too well… the Mail Spammer.

In the Spammers’ ongoing war against humanity they noticed that most people order their inboxes by the date that mails were received, and realised that if they sent mails from the future their mail would be much more likely to be at the top of your inbox, and therefore much more likely to be read.

BT & Yahoo’s response to the Spammer’s new trick was to simple reject any mail from the future, which is an effective but brute force approach. In the case of our customer, they fell foul of this filtering when they inadvertently changed their system date. This is quite easy to do accidentally in Windows XP – if you click the clock in the system tray and then change the date (maybe to find out what date a certain day falls on), then click ‘Apply’ rather than ‘Cancel’, you won’t be sending any more emails to Aunty Dot until the problem comes to light.

In contrast to BT & Yahoo’s approach we prefer to subject all our incoming and outgoing mails to purpose-built heuristics, filters and spam engines. It’s more processor intensive, more expensive, and to be honest it’s a lot more effort, but it’s part of trying to provide the best service we can. Which saves you money, and just as importantly saves you time.

 

Next post: What the web looked like 15 years ago

Previous post: Make your website social in 10 minutes