NC cannot send test mail with some account, but ok with one


I run NC on Infomaniak shared hosting. Install happened via Infomaniak console (“app”)
When getting to the “Basic settings” > “Email server setup” (required for password reminders etc), I introduced the credentials of an e-mail address hosted at Infomaniak (but domain managed at OVH).

When clicking on the “send mail” button, I get the following error: A problem occurred while sending the email. Please revise your settings. (Error: Email could not be sent. Check your mail server log).

I revised the settings, all was correct.
I then asked support Infomaniak to have a look, on their request , I created an account for them which is member of the admin group:

  • they could send a test mail without problem
  • logging in with the account created for them, I could also
  • logging in with 2 different accounts members of the admin group, I get the error message…

Any idea?


Nextcloud version (eg, 20.0.5):
Operating system and version (eg, Ubuntu 20.04): Debian
Apache or nginx version (eg, Apache 2.4.25): Apache
PHP version (eg, 7.4): 8.1