A lot of stuff comes per e-mail. But I have a problem to link it in a
database because it is lacking a URL, a unique ID and a way to access it
via web browser.

I'm now berating myself for neglecting to see this one for myself. That is so important. Thank you for expressing.

1. Read the message headers
2. Lookup message Id in the imported_messages table
3. If its not there we parse the message and remove the attachments (saving them to disk and linking them to the contact record)
4. We save the body of the message as a note under the contact record

There are a few other steps we do but that is the basic process to create a email aware contacts database.

Cheers

Piers