Airmail is an email client with a slick and modern visual design and built-in support for a wide range of apps, including OmniFocus. It’s touted as “having fast performance and intuitive interaction” and supports most email servers including iCloud, Microsoft Exchange, Gmail/Google Apps and IMAP.
Airmail for Mac
Using Airmail for Mac you can create an OmniFocus action that references the selected email using the Create OmniFocus Task feature. Select the email and control or right-clicking on the message or, more conveniently, press the predefined hot key ^⌥O. Either way, the Quick Entry window will appear with the title of the action set to the subject of the email by default and with a link to the message stored in the notes field. This link allows convenient access to the email from OmniFocus and will continue to work even if the email is moved to another folder, such as the Archive.
Additionally, the Mac version of Airmail allows you to create rules that leverage this OmniFocus integration. These rules can be triggered by the contents of the email and/or a hot key. For example, you could have a rule that is triggered by pressing ^S that creates an OmniFocus action for the selected email and then moves the email to the Archive folder. This integration opens up a wide range of possibilities for automation.
Airmail for iOS
Airmail is also available for iOS. Once configured, you can create an OmniFocus action that reference an email simply by choosing “Send to OmniFocus” from the action window The subject of the email is used for the title of the action, and the notes field contains both the contents of a message and a link to the email itself. Conveniently, this link will work on both Mac and iPhone versions of Airmail.