Thank you for your reply and suggestion.

I tried it, with Outlook 365 desktop version open, and I tried to send client checklist both with the "64-bit email client" checked and unchecked.

It keeps saying "email error"

I have had the same problem email tax returns or anything from ProSeries it started about 4 months ago with the 2018 version, and 2019 ProSeries is the same.