If I were to build a newsletter emailing system, I will need to be able to generate reports on how many emails bounced, flagged as spam, unsubscribed, read vs. unread, click through rates etc....
So how do you keep track of user activity after the email has been sent? Am I right in assuming that you CAN NOT embed javascript code into emails to monitor user activity? How else do I gather data for my reports?
Once you send the e-mail, it's free like a baby bird kicked out of the nest. The writers of e-mail clients go to great lengths to make sure that they block any feature that will give you that kind of feedback you're asking for. While there are legitimate uses for this sort of information, spammers use such information to verify and clean their e-mail lists.
Many ISPs also block bounces because they give spammers information.
The best you can do is try to give your readers an incentive to click through back to your site. Then, you can gather information not available to a sender of e-mail.
You can easily track click-through rates by including a tracking query string bit in the URLs and route them through your site.
So a link might be: http://mysite.com/?LinkID=foobar
As for read vs. unread you can get an idea for that by including a small transparent image from your site that includes a tracking URL http://mysite.com/track.gif?EmailID=email. However this is not foolproof since emails can be read offline and most modern email clients do not display images without a user action to display images in the email.
For bounced, you'll have to track those by reading from a mailbox for the From email.
Can't think of way to track emails flagged as spam except to send it to several mailboxes that use some of the common spam filtering products and check the results. However, this isn't likely to be accurate because most can and are customized/trained by individual users.
If you want to do click tracking you'll have to replace all links from your message with links that point back to your tracking script. To do efficient tracking that you can actually use later for segmenting your list and better targeting you would have to track the subscriber's id and message and/or campaign id. Some email marketing systems even track the link position in the message so you know exactly if the recipient clicked on the same link that was at the top of the message or in the middle and in the system that I have built I even track if they clicked a link in the html part of the message or the text part.
The tracker script would record all this information then redirect to the actual link.
Bounce tracking is done by processing the bounce messages that your server will receive or generate when a message cannot be delivered. I recommend using VERP: http://en.wikipedia.org/wiki/Variable_envelope_return_path
Open tracking is done by including the image with tracking code in the url. This would normally point to a script on your site that would record the subscriber id and message and/or campaign id then output the binary date for a transparent 1x1 px wide gif.
You can also track messages that are flagged as spam by some users of some ISPs like hotmail, yahoo, aol, and a few others. they offer feedback loops so every time someone clicks that "Spam" button in their webmail application they will send you a message that you can parse and determine the subscriber that actually flagged the message as spam. VERP also helps with this because the feedback loop messages don't always include the actual email address of the subscriber so you need another way to identify them. This page on wikipedia has a list of feedback ISPS that offer feedback loops : http://en.wikipedia.org/wiki/Feedback_Loop_%28email%29
