Using Classic Outlook on Windows for personal email, calendar, and contact management
Hi! On Windows 11, have you tried this? add the account manually as IMAP using imap.mail.att.net:993 (SSL/TLS) and smtp.mail.att.net:465 (SSL) or 587 (STARTTLS), username = your full email, and for the password use an AT&T “Secure Mail Key” (a 16-character app password created in your myAT&T profile) instead of your normal password.
Before retrying, sign in to webmail at currently.com to confirm the account works, make sure Secure Password Authentication (SPA) is unchecked, and remove any saved credentials in Control Panel > Credential Manager > Windows Credentials so Outlook prompts you again. iPhone sets up via OAuth automatically, but Outlook often requires the Secure Mail Key for these legacy domains.