Well I found a not too recent web posting on the web where the poster was having same problem with a Samsung. Apparently the outgoing port should be 25. Mine has always been set to 587 as per TT info. That has cured the problem, but for some reason when I go to settings it has reverted to 587 so has to be reset. No way to save the setting. Will go back to the Android forum and check.
Windows 10 Home vs Windows 10 Pro comparison: Here are the extra features you get in the Pro version