I encounter quite often a problem with Nextcloud eMail on Nethserver: If I want to share a link, I need to setup up the eMail host correctly. I did that using Nethserver as a smarthost, test mail works fine. But from time to time, something goes wrong, I can not send the share eMails anymore. Than I need to go to the admin login, change some settings for the smarthost until everything works again and than it works for a few weeks. After some days / weeks … the problem reoccors.
Sorry, I did not note the exact settings for smarthost when the error orrurs, but here is the current, working setup
I know, in some weeks I will e.g. switch to “no aut” or “STARTTLS”, with / without authentication
NethServer Version: 7