Yes, The Windows version of NXPowerLite can automatically reduce email attachments but the Mac OS X version does not have this functionality.
NXPowerLite Desktop (Windows) can optimize file attachments automatically and has plugins/add-ins to the following email clients:
- 32 & 64 bit versions of Outlook 2002-2016
- Lotus Notes (6.0 - 9.x)
- Outlook Express (6.0+)
Please note: Automatic zipping of emails is only available for Outlook 2010, 2013 & 2016