There are a couple ways to go about checking if a message has been read but
these methods have pro's and con's. I will list them in order. I will
assume that by "became them" you meant "read them."
1. Do not email them the actual message just e-mail the user a URL that
points to a script on your server. Then when they open the link your script
will update your database and show the message. If the user never clicks
the link you can assume the message was not read. The problem with this is
they may be reading the message off line or using a mobile device and not
have web access, so not only will you not be notified but the user may not
be able to read the message.
2. Try and capture all the failures and assume that the messages that didn't
fail were delivered and read. This of course is a large assumption. Take a
look at the below article on this. The article is about cleaning your
address list but the same technique can be used to log failures in your
database.
http://www.quiksoft.com/newsletter/issue001/
3. Send an HTML message and put a 0 size image tag that points to a server
script. The image URL should URL with parameters that will be passed to
your script. i.e. <img src="
http://myserver/logger.aspx?user=x&msg=y"
height=0 width=0>. Then your script should get hit when the message is
read. The problem with this is not everyone's browser supports HTML and
some of the ones that do won't go out to the web and load images.
4. Adding a read receipt to the message. If you add a certain header to all
the messages going out some mail clients will see the header and return a
read receipt. The problem with this is most mail clients prompt the user
before it's sent so they can choose not to send it and some clients don't
support the header and it is ignored.
As you see nothing is 100%, you may also be able to combine some of these
tricks and hope that at least one of them succeeds. Please let me know if I
missed anything.
Bill
