I see. That's a lot more complex than what I did even when I was reaching out to our 45K members. For this many members I didn't use Constant Contact but instead went to PM only distribution. I did this for a couple of reasons:
- richer formatting of the message
- no opt in/out was needed since the message stayed within the confines of the service I was offering
- no blacklisting would happen
- it would generate email based notifications for the majority of our users so even if they haven't been on the site in a while it would entice them back on if they were still interested (Note: for registration options I always had email notifications set for private messaging as the default)
The only problem we ran into with this approach was that even with some modifications I had made to a bulk private messaging tool (this was back on
vB 3.6.1) it would load the system quit severely and would sometimes fail at some point before making it through the entire user population.
To build something that would offer tracking, PM and email versions from the same content, etc. would be pretty involved but would offer some good flexibility over what is currently offered in the stock vBulletin functionality.