Integrate mail into Nextcloud

I entered the mail facility in my Nextcloud and tried to configure my email address. That failed:
Error while creating the account: Creating account failed:Mail server denied authentication.

What is going wrong?
In nextcloud.log I see these line:
{“reqId”:“uBOR3zF83EA5XBDPZdoa”,“level”:3,“time”:“2017-11-21T15:40:04+00:00”,“remoteAddr”:“”,“user”:“secret”,“app”:“mail”,“method”:“POST”,“url”:"/index.php/apps/mail/api/accounts",“message”:“Creating account failed: Mail server denied authentication.”,“userAgent”:“Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.94 Safari/537.36”,“version”:“”}

(my mail account name is now displayed as ‘secret’)

What is going wrong?

Guido van Harten

Looks like wrong Account Info

Mail server denied authentication

I retried and retried, changed the password, and suddenly it works well. I still don’t know why it was not working the first time.
Thanks for helping.