Unable to SEND email using Mail app on new iMac
I have a new iMac running Mojave and am unable to SEND email using the Mail app. I am asked for the password for my apple account, and am told it isn't good even though the same password accesses everything else I try on this machine, my MacBook Pro, iPad Pro, iPad Air2, iPhone, etc. Does anyone have any idea what the problem might be? I am able to RECEIVE email sent to my .Mac address. Thanks, I appreciate any help you might be able to provide. - Roy
iMac 27", 10.14