Some user mailer fixes

I18n for mail subject
Host is omitted on calling mail method because we have the default
one...
Merge branch 'hotfix/mailer-fixes-1'

* hotfix/mailer-fixes-1:
  Some user mailer fixes
Merge tag 'mailer-fixes-1' into develop

v1.94

* tag 'mailer-fixes-1':
  Some user mailer fixes