Mail notification doesn't work anymore upgrade 8.12.7

Hello,

I updated my system (centos 7) and gitlab Omnibus package to 8.12.7
email notification doesn’t work anymore for users .
sending mail from shell does works fine
I tried to set
gitlab_rails[‘smtp_enable’] = true
and other smtp settings in /etc/gitlab/gitlab.rb (the reconfigure/ restart) , no way :frowning:
is it nececesary to set those smtp parameters ?
is there a bug or am I missconfiguring my gitlab instance ?

I googled related topics , but no succes neither
http://stackoverflow.com/questions/29463807/sending-emails-with-gitlab-not-working-correctly
https://gitlab.com/gitlab-org/omnibus-gitlab/issues/1283
http://stackoverflow.com/questions/36201390/how-can-i-configure-the-smtp-server-running-for-gitlabomnibus-which-running-on

regards .