In an interview with Direct Mag, email deliverability guru Laura Atkins provides these tips on how to monitor email deliverability:

1. Sign up for Feedback Loops (here's a current list of available FBLs). For small senders, the FBL may be able to be processed by hand. Medium-size senders may need to develop some tools for processing ARF messages.
   
   
2. Check free reputation monitoring sites such as Sender Score and SenderBase to identify if there are any reputation problems.
   
   
3. Monitor delivery logs to identify if any ISP is blocking outright [5xx responses]. This will also show rate limiting [4xx responses], which often is the first sign of a problem at a specific ISP.
   
   
4. Set up dedicated accounts at major ISPs—Yahoo!, AOL, Gmail, and Hotmail—and add those accounts to every mailing. You can also talk to employees and determine if they have accounts at some of the for-pay ISPs and would be willing to designate one of their e-mail addresses for business use.
   
   
5. If the senders continue to have problems they can either hire a consultant to help them identify underlying issues causing delivery problems or go to a certification service.

I highly recommend reading the entire interview here.

In this post, Campaign Monitor's Ros Hodgekiss explains how to get a repeating background image to surround your content in most major email clients, including Gmail and Outlook 2007! 

There are some very clever coding tips in the article, so if you're into coding, make sure to check it out!

Litmus has been examining the data they've collected from their new Email Analytics tool and found that on average, 51.1% of readers spend less than 2 seconds looking at your email.

Source: Litmus