I'll quickly explain what exactly I mean by list hygiene. You're sending out a newsletter to roughly 20,000 people. Some of these people have been signed up to your list since 2005. The only thing is, your email marketing lapsed for a little while and you haven't sent out an email in 6 months. But you've decided that the Christmas period is a great opportunity to start again.

So your Christmas campaign starts to go out, but you haven't set-up a proper email bouncing address. The email bounces for no longer valid email addresses flood into your inbox and instead of removing them from your mailing list, you just delete the notification email.

This is now leaving your list 'unclean' and can be very dangerous as you are running the risk of one of those addresses becoming a "spam trap". There is a full article on spam traps here but in short spam traps are set up by main email hosting companies such as hotmail or yahoo. These are addresses that have been set up and not used, and haven't had their details given to any companies so that any marketing emails sent to that address can be singled out as illegal emailing and the companies doing it can be blacklisted.

The problem is that hotmail and yahoo also use accounts that used to be live but have since become inactive and been deleted. This is where your 'unclean' list can come and bite you. If you happen to have one of these once inactive, now spam trap email addresses in your list you could be heading for the blacklist. This could mean that you would be blocked by one of the major email hosts such as hotmail, which for some companies is a large proportion of their list. In turn you will see your deliverability rates severly decrease and that will lead to poor open rates and click-through rates.

At this point your whole email list is then in trouble. You will probably have to resort to drastic matters such as sending out a re-permission email to get all legitimate names and recreating your email list from scratch. This will of course mean losing a lot of legitimate email addresses as people will not bother to sign up again.

So the moral of the story is?.

Don't be lazy when it comes to processing bounce addresses. That list needs to be clean so that you can build up a legitimate and successful email campaign and avoid falling into a spam trap.