Thank you for your post.
1. Yes, FileMaker Pro can handle/manage lists of 10-20,000 names. Recently, a file was sent to me with 8,000,000+ records.
2. FileMaker Pro will NOT develop an HTML email. There are third-party plug-ins that will allow rich text formatting when sending emails.
3. Yes, you can find a subset of records and send emails to only that subset.
4. This is a loaded question. You can definitely create a log of who was sent an email message. However, FileMaker Pro does not have the ability to see who has opened it. If they click on something that is registered somewhere, then if that data can be exported to a text file, FileMaker Pro can import it and update the record.
5. Yes, there are many types of reports, including summarizing by a group or for the entire found set of records.
6. I'm not sure what you mean my unsubscribes. Is this by email? By web site? If by email, then you'll need a plug-in to capture that data and import into FileMaker Pro.
7. Yes, you can "De-duplicate" the contacts, but you need to specify what you need to de-duplicate. For example, "J. Smith", "Jon Smith", "Jonathan Smith" may all be the same person, so you'll have to create the criteria to determine which is correct.
If you need clarification for any of the above steps, please let me know.