What email client application is installed on this machine? That's an important detail the TS personnel will need to know in order to have better chance of understanding the problem.
They were using Microsoft outlook as the email reader and Google email as the provider.
That makes this a known issue.
For More Information see: FileMaker 14 64 Bit and Send Mail via Email Client Outlook 64 Bit Not Working
This is one of many acknowledged bugs that can be found in the Known Bug List thread here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: https://www.dropbox.com/s/jt09b82i0xijbu3/FMP%20Bugs.zip
Thank you for your posts.
The answer from PhilModJunk is correct (Thank you!). Our Development and Testing departments are already aware of this issue, and we recently announced that this would be fixed in the next release. Please see the forum announcement "FileMaker Pro 14 and FileMaker Pro 14 Advanced update planned for August":