Segment your e-mail housefile

Caveats

Avoid the temptation to over-segment your e-mail database; this makes it difficult or sometimes impossible to track the resulting campaign data. If you’re working with a housefile of 100,000 names, says Brady, 100 segments might be overkill, but five would be manageable and easy to track.

Also be wary of certain domain names. Brady says customers whose e-mail addresses belong to free providers such as Yahoo! and Hotmail often use this address as a catch-all for junk e-mail. In other words, they may never check the account, so they may not be worth segmenting out.