I don't know of a sure-fire way, but most of the newsletters that I receive (I don't send bulk emails) ask that you put their address in the address book. I assume that some (most/all?) email programs don't block emails from users in the address book.

we have noticed that most of these newsletter emails are getting delivered to the Junk Mail / Bulk folder.

In what program or spam filter? For SpamAssassin, there is a setting to put all SA headers into the email so you can see how it's scoring. There are also a few "test" pages on the web that you can drop your email into to see what it's SA score is.

Unfortunately SA is only *one* system but it's well-used, get your SA score under 3 or 4 and you will be able to get most of them into other accounts. Well, except Gmail, haven't cracked that one yet (for legitimate emails.)

opt in newsletters

make it double opt-in.
That makes, imho, the subscriber more aware to getting mail from you. Also you get a cleaner email list with valid email adresses only.

Entering the senders email address in the addressbook only helps with onlineservices (like MSN, hotmail, yahoo) I think. It automatically whitelists the sender.

In additon to the above, make sure that your sender address as well as your subject line are telling the receiver what to expect. Dont send email ad John Doe when you are known as contentmaster. Make your subjectlines clear e.g. like: Contentmaster News August 20.
Hope this helps you improving your mailing campaigns.

You might find some important info on this thread "EOC" [webmasterworld.com]

Habtom

I will be looking into all that has been mentioned - Thanks!