gitlab-ci not sending email on build failure

Summary

Email notifications are not sent when a build fails.

Steps to reproduce

Cause a build to fail.

Expected behavior

The user who caused the failed build should receive an email, per the default GitLab CI setting gitlab_ci['gitlab_ci_all_broken_builds'] = true in /etc/gitlab/gitlab.rb. All other GitLab email notifications work as expected. The GitLab email settings in gitlab.rb are the same as the GitLab CI email settings.

Relevant logs and/or screenshots

No mail attempts are being logged to /var/log/mail.log for failed builds. Other Gitlab email notifications are logged.

Output of checks

Results of GitLab Application Check

Checking GitLab Shell ...

GitLab Shell version >= 2.6.9 ? ... OK (2.6.9)
Repo base directory exists? ... yes
Repo base directory is a symlink? ... no
Repo base owned by git:git? ... yes
Repo base access is drwxrws---? ... yes
hooks directories in repos are links: ... 
5/2 ... ok
5/3 ... ok
5/4 ... ok
5/6 ... ok
5/7 ... ok
5/8 ... ok
5/9 ... ok
5/12 ... ok
Running /opt/gitlab/embedded/service/gitlab-shell/bin/check
Check GitLab API access: OK
Check directories and files: 
	/var/opt/gitlab/git-data/repositories: OK
	/var/opt/gitlab/.ssh/authorized_keys: OK
Test redis-cli executable: redis-cli 2.8.21
Send ping to redis server: PONG
gitlab-shell self-check successful

Checking GitLab Shell ... Finished

Checking Sidekiq ...

Running? ... yes
Number of Sidekiq processes ... 1

Checking Sidekiq ... Finished

Checking Reply by email ...

Reply by email is disabled in config/gitlab.yml

Checking Reply by email ... Finished

Checking LDAP ...

LDAP is disabled in config/gitlab.yml

Checking LDAP ... Finished

Checking GitLab ...

Git configured with autocrlf=input? ... yes
Database config exists? ... yes
Database is SQLite ... no
All migrations up? ... yes
Database contains orphaned GroupMembers? ... no
GitLab config exists? ... yes
GitLab config outdated? ... no
Log directory writable? ... yes
Tmp directory writable? ... yes
Uploads directory setup correctly? ... yes
Init script exists? ... skipped (omnibus-gitlab has no init script)
Init script up-to-date? ... skipped (omnibus-gitlab has no init script)
projects have namespace: ... 
5/2 ... yes
5/3 ... yes
5/4 ... yes
5/6 ... yes
5/7 ... yes
5/8 ... yes
5/9 ... yes
5/12 ... yes
Redis version >= 2.8.0? ... yes
Ruby version >= 2.1.0 ? ... yes (2.1.7)
Your git bin path is "/opt/gitlab/embedded/bin/git"
Git version >= 1.7.10 ? ... yes (2.6.1)
Active users: 10

Checking GitLab ... Finished

Results of GitLab Environment Info

System information
System:		Ubuntu 14.04
Current User:	git
Using RVM:	no
Ruby Version:	2.1.7p400
Gem Version:	2.5.1
Bundler Version:1.10.6
Rake Version:	10.4.2
Sidekiq Version:4.0.1

GitLab information
Version:	8.3.2
Revision:	fbb8b6e
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	postgresql
URL:		https://git.<removed>.com
HTTP Clone URL:	https://git.<removed>.com/some-group/some-project.git
SSH Clone URL:	git@git.<removed>.com:some-group/some-project.git
Using LDAP:	no
Using Omniauth:	no

GitLab Shell
Version:	2.6.9
Repositories:	/var/opt/gitlab/git-data/repositories
Hooks:		/opt/gitlab/embedded/service/gitlab-shell/hooks/
Git:		/opt/gitlab/embedded/bin/git