Using New Outlook on Windows for personal email, calendar, and contact management
hi james, welcome in community
you should edit the smtp settings and enable the authentication for smtp. you can find it in outgoing server tab > flag the voice "My outgoing server (STMP) require authetication", maintain "Use same settings as my incoming mail server", under advanced tab you must insert the port suggested by your mail provider (usually 110/587)
let me know how it goes
Elvis