[SpiralOcean]

Here is how you would do it:

In OmniFocus, open the preferences.
Click on the Mail option.
Check the
Add Mail Rule to create OmniFocus Actions.
close the preferences

go to Mail preferences
click on the Rule option
select the 'Send to OmniFocus' rule
click on the edit button
change the first condition from
Any Recipient contains +omnifocus
to
Every Message

You may also want to remove the Delete Message action from the actions.
click OK to save

One note about doing this.

It will make it very difficult to reply to messages. This is because the current Applescript that is clipping the mail to OmniFocus, does not include the link to original message in the OmniFocus action.