include example mailer options. Fixes #3171
This is a resubmission of #3851
Coverage decreased (-0.03%) when pulling 2497012 on slide:master into 78ff99a on gitlabhq:master.
@randx can you take a look?
THank you for PR.
However this does not makes sense for me. We have config for host/port in gitlab.yml.
If somehow it not applied to all cases we should find why and add appropriate fixes.
Duplicating host settings is not a best way