Airmail can integrate with Droplr. To enable the Droplr integration, please go to Airmail Preferences > Services and then 'Sign in Droplr' as shown in the picture below.
You can save the files and create links(drops) on Droplr (as .pdf files) and attach the files from Droplr in the Airmail composer.
How to save a message to Droplr from Airmail?
Please follow these steps.
1. Right click on a message and select 'Send to' or just press the 'Z' shortcut key to open up the share menu.
2. Then choose 'Save to Droplr' as shown in the picture below. You can also configure 'Save to Droplr' as a 'Menu Button'.
This will allow you to create a 'Droplr' link/drop and you can share it as per your requirement.
How to attach using Droplr?
You can attach using Droplr in Airmail Composer as shown in the picture below:
Once attached and the upload finishes, a link will be created on your linked Droplr account as shown in the picture below: