Configuring preferences and options in Outlook.com
OK - I've had enough. I give up! Not only does Outlook User Storage keep shooting up to cause the phone's storage to hit 100% every few days, it now starts refusing to send e-mails. The new message is "Outgoing server error - cancel or update." The "update" option shows that the outgoing Mail server port number has been overwritten with the incoming IMAP server port number. Correcting it doesn't work - it stays stuck on the wrong number.
Outlook mobile really is a load of cr-p. It used to work fine until about the end of 2020. I don't know what Microsoft has screwed up.