SMTP - NTLM authentication problem

Summary

I'm using Omnibus package with Gitlab CE. I need to connect Gitlab with SMTP exchange server, which supports only NTLM authentication type. According to https://gitlab.com/gitlab-org/gitlab-ce/issues/2408, I'm not first person, who face this issue. Do You know any way to install ruby-ntlm into Gitlab?

Steps to reproduce

Configure Gitlab CE to connect with SMTP, which supports NTLM authentication.

Expected behavior

NTLM is supported.

Actual behavior

NTLM is not supported, error: ArgumentError: wrong authentication type ntlm