Start Outlook (desktop app) — not “new Outlook” or Mail & Calendar.
Go to File > Add Account.
Select Manual setup or additional server types.
Choose POP or IMAP.
user@yourdomain.com
stratamailxxx.mailshelter.com
xxx
Go to More Settings > Outgoing Server ? check My outgoing server requires authentication.
Go to Advanced:
IMAP: 993, SSL
SMTP: 465 (SSL) or 587 (TLS)
Click Next, Outlook will test the connection.
If successful, click Finish.