OK, now I have two problems:
The first is that I need to grant write privileges to the webserver for temp/ and logs/. I don't know which command to use and how. The following is what appears on the php installer:
Check if directories are writable
Roundcube may need to write/save files into these directories
temp/: NOT OK(not writeable for the webserver)
logs/: NOT OK(not writeable for the webserver)
Use chmod or chown to grant write privileges to the webserver
The second problem concerns the mail server. I don't really know how I can get a working imap and smtp. For info, my domain is cervoni.info, my hostname (FQDN) is mail.cervoni.info. On my dns service, I have both an A and MX record for mail.cervoni.info.
How I can get mail for a user (with the right logins), say the admin for instance, is what I don't understand.
Thanks for your help.