problem with sending mail with Catalina
Since upgrading to Catalina on Mac Powerbook 2012 I can't get mail to send reliably (and message just sits in Outbox). Receives OK, but typically requires Quit and reopen mail to send. Does this with mail accounts from all email accounts (gmail, iCloud etc). Have spent over 8 hours with apple support doing everything from deleting and adding mailboxes, trying to add server info manually, reinstalled Catalina two days ago, etc. I have another Powerbook (1 year older) running High Sierra and everything works perfect. Mail work perfect on iPhones as well. Last agent basically said there is nothing more they have to try and it appears Catalina mail seems to have an issue and I need to upgrade OS (which I can't do on this machine). Surely I am not the only person trying to use Apple mail app with Catalina 10.15.7? Anyone else running such successfully? Anyone else having similar issue or had the issue but resolved it? Please, please help.