I am using FileMakerPro 14.0.4 on a Mac with OS 10.11.1
Every couple of months I have to email about 250 members with an attachment of about 400KB I can now no longer get any size of attachment to attach. All appears well - the emails arrive at their destinations, but without any attachment. I have always used Mail as my client. I have tried a variety of ISPs and several available accounts - Apple's have always been the most reliable.