Trouble with Authentication Method : CRAM-MD5

my mail server for gaming uses the autentication method CRAM-MD5

For some reason there is no authentication setting for IMAP in /etc/gitlab/gitlab.rb like it is for smtp in line 86 :

gitlab_rails['smtp_authentication'] = 'CRAM-MD5'

so I tried to add :

gitlab_rails['incoming_email_authentication'] = 'CRAM-MD5'

but I was not successfull ...

and after I run gitlab-ctl reconfigure

I couldn't see any settings according the authentication in /opt/gitlab/embedded/service/gitlab-rails/config/gitlab.yml around the line 136 and below. Could this be the reason why I cannot log in ?