You might want to check out the following threads on the forum in which I have posted an applescript that will send an HTML formatted email to DevonThink from Airmail with links back to the original message in Airmail along with an applescript that will send attachments from Airmail to DevonThink. I just have an Alfred workflow that triggers the applescripts with a keyboard shortcut.
[url]Airmail to DTTG using new URL scheme]
[url]Airmail 3]