getting email newsletters right

I have over the years subscribed (either intentionally, or been 'forcefully' subscribed) to a lot of email newsletters. Having also been involved in creating and sending out newsletters by email, I've recently been mulling over how to get them right - from both ends.

My ideas on keeping your subscribers happy:

• Always provide multipart emails (a combo plain text and html email) - not everyone enables html emails, and a lot of people consume emails in multiple platforms as well, so make sure you provide both
• Don't overdo it - site marketing only needs to come out every two weeks to once a month - any more than that, and I feel like I'm being spammed. If I want to know about every new deal or update to your site, I'll probabaly subscribe to your RSS feed
  
• Set up some good tracking links if you're interested in tracking conversions or hits based on an email - google analytics is dead easy, and can track and report on most of the info you need. Either use this method from Think Vitamin of adding query string parameters to your links, or set up referral redirects, all depends on your setup - tho if you use redirects, make sure they either 'live forever', or get a process up and running to replace those redirects with something more relevant in the future
• Make it timely - fine tune your sending mechanism to be fast, fast, fast! If you take a week to send out the mails, a lot of your content may now be out of date. Find the most efficient way to get those mails out fast
  
• Find out what platforms your target audience uses, and go with a design that works for that platform - there isn't a perfect formula for doing HTML emails that work 100% of the time, but if 50% of your possible (or current!) subscribers use Lotus notes or other clients that don't support full css, you're probabaly stuck with the terror of the old HTML tables. If 80% are only consuming the plain text versions, then don't invest days of work on nice html or graphics. Put your css styles in the body of the mail to support Hotmail
• Don't make the plain text consumers feel like the poor cousin! I've seen multipart emails that have a rich, content full HTML version, yet just a link to an on-line version of the mail for the plain text version
• So you've lost their interest, let them go! Always provide a one-click unsubscribe link, or a unsubscribe email address, which is easy to find in your mail. Don't make your subscriber sign into a site they probabaly can't remember their password for, don't keep sending out 'why are you leaving' emails or three step unsubscriptions. Make sure your unsubscribe process works, and takes effect as soon as possible (I've had a lot of cases where an unsubscribe email either bounces, or is totally ignored), or you might get accused of spamming