Hotmail and Other Services Have Many, Many Spamtraps

Legitimate email marketers need to deal with old email addresses that persistently return nondelivery reports. This isn't news, but here's another reason why...

Hotmail accounts expire after six months of disuse. This happens often -- people sign up for accounts and then soon stop using them for a variety of reasons. For example, users may think they need an account to use the MSN Messenger IM system, or maybe they're using Hotmail temporarily as a throwaway address (to give to vendors they don't trust).

Once a Hotmail account expires, mail sent to it will be rejected, normally with 550 Requested action not taken: mailbox unavailable. After a further six months (i.e., one year of disuse), the mailbox may be treated as a spamtrap. This means that email sent to old Hotmail addresses may be used as samples to help train spam filters for Hotmail, MSN, FrontBridge, the Outlook Junk filter, etc.

Microsoft is by no means unique in doing this, but it's said that it is more aggressive than most.

What does this mean for legitimate marketers? It's now more important than ever to detect and eliminate bounces from your lists. If a receiving mail system consistently tells you that an address is bad, remove that entry from your lists. If you don't, your IP range can be blacklisted and/or your message content will seem more "spammy." Of course, this means that your messages are more likely to end up not being delivered to your users.

It used to be simply bad manners for a sender to continually send mail to nonexistent addresses, but now it's actually self-destructive.

... Richi Jennings, with thanks to Ben Isaacson of Experian/CheetahMail and Justin Mason of the SpamAssassin project

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