Sorry for the trouble! When you clip a message into OmniFocus from Mail.app, we use the message’s unique ID to create a link back to the message. That said, if Mail.app changes that unique ID it will break the link to the original message. The most common way to trigger Mail.app to assign a new ID is to move the message to a different folder.
You can verify that this is the issue by comparing the message’s ID in OmniFocus and Mail.app:
In OmniFocus:
Right-click on an Original Message link
Select: Edit Link
Take note of the ID string in the <angel brackets>
In Mail.app:
Select the same message
From the Menu Bar, select View > Message > All Headers
In your email header, note the value for the “Message-Id” field
If there’s a different ID in Mail.app, then it means Mail.app has changed the ID since the link was created. I’m afraid there’s nothing we can do about this from our end, sorry! I would recommend moving the message to your @action folder in Mail.app first, then clip to OmniFocus in order to avoid this scenario.
tried your suggestions, and, yes, the mail ID is just the same, but after clicking on the Link in OF an empty message with the rigt message title is opened.
The messag title has the appendix “- Eingang” (= “- Inbox”) in the title bar, so it seems that Mail tries to localize it inthe Inbox folder.
Apologies, but it sounds like you’re encountering a known bug with Apple Mail. We’ve found that quitting and relaunching Mail may resolve this temporarily, but a permanent fix will need to come in the form of an update to Mail. If you’d like to connect with Apple in regards to this issue, we’ve filed this radar with Apple in their tracker as: rdar://problem/6320591.