Hello,
When you view the list of e-mails, there's an action button for each email, that looks like this:
Clicking that icon will put the mail in a sort of "clipboard". You can then view any other record with an e-mail addon, switch to that addon and a "Paste mail" button will appear on actionbar (this button will be moved onto the addon panel for consistency, in one of the upcoming releases).
Clicking that button will create a "link" between the mail and currently displayed record. Any previous links are preserved, so your e-mail will be linked with 3 (or more) records.
Hope this helps,
Arek
