I am using Nextcloud as an end-user with no admin access. When I change the login password from the default password to a new password, my email no longer functions: new messages cannot be loaded (and sometimes the inbox and all the messages disappear altogether - the inbox disappearance occurs apparently on a random basis). As soon as I change back to the default password, this issue disappears and the email functions normally. However, it is clearly unacceptable in any system to be unable to change one’s login password, so I need to find a solution.
You will need to talk to your Nextcloud system admin about that because Nextcloud is not an email server (it can only work with an external email server), and I have no idea what that system is or how it’s been set up.
Many thanks KarlF12 - this is very helpful.