I have Lightroom Classic on my iMac (OS 10.14.6) and it has stopped exporting a photo to email. Several of the export options are no longer working. I can select export to email and I get the right screen and pick what size I want the photo sized to, and then the activity bar top left tells me it is preparing the photo and them it goes away and just stops. No email is created. I've have restarted LR, restarted my mac, uninstalled LR and reinstalled it. Still no solution.
I went back to the 9.4 release and all worked fine. This is an Adobe issue and not me here I think. I'll not move to a 10 version until they have things worked out. They say they got a fix in 10.1 but must not have done so for my configeration, as my 10.1.1 sure didn't work.