B2B online, has an article called: What can I do to re-engage inactive subscribers on my e-mail list?

The article suggests the following:

• Pull inactive subscribers into a seperate list
• Pull your data together and look for patterns in inactive subscribers
• Develop new email offerings
• Change subject lines
• Change from address (but not the domain)

One thing to keep in mind is that there is no way to know for sure if a person has read an email. Many email clients will block images by default, which are often used to determine if a person has read the email.

Another thing about changing the from address, this may cause email to go directly into the spam folder on challange response email systems (systems that use a whitelist, and require human verification) - if you don't have a system in place to deal with challange response verification emails, you may not want to do that one. You might first try changing the From name.

Our XMS Email Server bounce plugin does recognize challange response bounces, and can forward these bounces to another address so you can have someone go through and validate your legitimacy.