Changed SMTP server of forum.fair.coop
Till now we were using a gmail onpurpose created account while we were waiting till we have new mail.fair.coop out of shit5 servers.
Bcs of some firewall issue and thnks to @berzas to find out... we had to use the IP instead of the 100.vps.fair.coop the real IP
so discourse/htdocs/config/discourse.conf became
smtp_address = '10.81.228.100'
smtp_port = 25
smtp_domain = 'mail.fair.coop'
smtp_user_name = 'forum@fair.coop'
smtp_password = 'xxxxxxxx' (hidden)
smtp_enable_start_tls = false
authentication = plain
smtp_authentication = plain
and now works fine and not mails will go SPAM or will get rejected like before.