What is the preferred way to send newsletters?

[stanj]

We are an incoming tourism service provider and I need to send out monthly newsletters to clients who booked tours with us for the summer of 2007 that keeps them up to date on their excursions.
What is the preferred method to send these out without being tagged as a spammer? I tried sending one of the newsletters as a test to one of my own email accounts, just one copy sent, and it was rejected as spam when sending it. Now sending any message from the same account fails by being tagged by Spam-Cop. I am not sure how that could be, the one newsletter west sent from out main business account to my personal account on the same domain. How did it determine it was spam?
Just looking for options, any leads will be appreciated.
Thanks
Stan

[dpyers]

The Spam Assassin site has a list of the points it assigns for things it finds in an email. The list is a pretty good guide for what not to do.

Won't help you with places like AOL though who maintain their own block lists based upon users designating an email as spam.

Use a double-opt in mail list - they sign up, and then you send them a confirmation email that they have to respond to. Also, log the response date/time/ip in case of a dispute. Vortech imposes severe penalties if you're reported as a spammer, so it helps to have proof that someone signed up.

Make sure your list members know they signed up for a mailing list... it's one thing for a company to be able to contact me for a specific instance. It's spam if they then send me a news letter I didn't know I would be getting.

Make sure they can opt-out. I had a large organization blacklisted because their opt-out didn't work.

Don't send email in blocks to any one mail provider. Places like AOl, Yahoo, MSN flag email as bulk if they see a lot coming in at once from one ip. Matter of fact, a lot of lists won't allow a user to sign up using AOL, MSN, or Yahoo email accounts because of delivery problems.

Vortech will only allow 2000 emails a day from any one VT hosted address. You can submit a TT to get put on a whitelist for more than 2K emails/day.

[stanj]

Thank you for the responses. I've never done any mass mailings and in this case it is not promotion but part of what the client has already paid for so I am not sure how opt-it effects this in that the updates are part of the sale supplying information needed to complete their program, information not available when they booked. For example this issue(the first) detailed the new visa law that has just changed and they need to follow it or else not be able to get off their ship.
What I did not understand in this case was the single test I did was to send a single copy, consisting of a text article and instructions, only to my own account on the same domain and that was enough to get my account blocked overnight. I sure did not report it as spam. My own mailbox of course is filled with hundreds of spam messages a day.
I do not want to use email for marketing and promotion, I do not think it would be effective for my field, I just want to communicate with subgroups of our clients who have not arrived here yet. If there is a better way to do this I would sure like to hear about it. This information only needs to go to the group leaders and not individual tour members. I post it on a members section of the web site but I need to tell them the information has been posted.
Thanks
Stan

[DaveMBush]

Everyone who is anyone doing email marketting will tell you to use AWeber. Reasonable monthly fee and tools that help you implement everything dpyers outlined and they do the work of keeping the mail IP off the black list.

I don't have an account with them myself only because I don't do email marketing, but if I did, they'd be my first choice.