Emails dropped without any errors or spooling when sendmail is configued
Yesterday after upgrading to 8.9 RC5, we noticed an odd thing with the Rails configuration: it was configured to use sendmail instead of SMTP:
irb(main):009:0> ActionMailer::Base.delivery_method
=> :sendmail
irb(main):010:0> Gitlab::Application.config.action_mailer.delivery_method
=> :smtp
RC3 did not have this problem.
We still do not know the issue, but we added a setting in gitlab-org/omnibus-gitlab!826 (merged) to resolve the issue.
I'd still like to know why sendmail didn't show any output, errors, or warnings anywhere, and the Sidekiq task for sending mail appeared to succeed:
2016-06-17_02:04:44.35679 worker1 sidekiq: 2016-06-17T02:04:44.356Z 23391 TID-1dhrck ActionMailer::DeliveryJob JID-835e021a719df1beb648df8a INFO: start
2016-06-17_02:04:44.36312 worker1 sidekiq: 2016-06-17T02:04:44.356Z 23391 TID-1dhrck ActionMailer::DeliveryJob JID-835e021a719df1beb648df8a INFO: arguments: [{"job_class"=>"ActionMailer::DeliveryJob", "job_id"=>"1c0401f5-6378-4a73-9aa0-7dca37a9d28f", "queue_name"=>"mailers", "arguments"=>["Notify", "note_merge_request_email", "deliver_now", 538661, 12516369], "locale"=>"en"}]
2016-06-17_02:04:44.60569 worker1 sidekiq: 2016-06-17T02:04:44.605Z 23391 TID-1dhrck ActionMailer::DeliveryJob JID-835e021a719df1beb648df8a INFO: done: 0.249 sec