DEV: replace mailcatcher references with mailhog (#14500)

DEV: replace mailcatcher references with mailhog (#14500)

diff --git a/config/environment.rb b/config/environment.rb
index ce160dc..516a139 100644
--- a/config/environment.rb
+++ b/config/environment.rb
@@ -8,5 +8,5 @@ Discourse::Application.initialize!
 
 # When in "dev" mode, ensure we won't be sending any emails
 if Rails.env.development? && ActionMailer::Base.smtp_settings != { address: "localhost", port: 1025 }
-  fail "In development mode, you should be using mailcatcher otherwise you might end up sending thousands of digest emails"
+  fail "In development mode, you should be using mailhog otherwise you might end up sending thousands of digest emails"
 end
diff --git a/config/environments/development.rb b/config/environments/development.rb
index 7e58350..bb6b7a9 100644
--- a/config/environments/development.rb
+++ b/config/environments/development.rb
@@ -42,7 +42,7 @@ Discourse::Application.configure do
 
   config.handlebars.precompile = true
 
-  # we recommend you use mailcatcher https://github.com/sj26/mailcatcher
+  # we recommend you use mailhog https://github.com/mailhog/MailHog
   config.action_mailer.smtp_settings = { address: "localhost", port: 1025 }
 
   config.action_mailer.raise_delivery_errors = true
diff --git a/config/environments/profile.rb b/config/environments/profile.rb
index d09ddcd..66baaaa 100644
--- a/config/environments/profile.rb
+++ b/config/environments/profile.rb
@@ -29,7 +29,7 @@ Discourse::Application.configure do
   # Specifies the header that your server uses for sending files
   config.action_dispatch.x_sendfile_header = 'X-Accel-Redirect' # for nginx
 
-  # we recommend you use mailcatcher https://github.com/sj26/mailcatcher
+  # we recommend you use mailhog https://github.com/mailhog/MailHog
   config.action_mailer.smtp_settings = { address: "localhost", port: 1025 }
 
   # Send deprecation notices to registered listeners
diff --git a/docs/DEVELOPER-ADVANCED.md b/docs/DEVELOPER-ADVANCED.md
index 95f0295..6ad004b 100644
--- a/docs/DEVELOPER-ADVANCED.md
+++ b/docs/DEVELOPER-ADVANCED.md
@@ -24,7 +24,7 @@ To get your Ubuntu 16.04 or 18.04 LTS install up and running to develop Discours
 
     rvm install 2.6.2
     rvm --default use 2.6.2 # If this error out check https://rvm.io/integration/gnome-terminal
-    gem install bundler mailcatcher rake
+    gem install bundler rake
 
     # Download and install postgresql-10 from https://wiki.postgresql.org/wiki/Apt
 
@@ -75,9 +75,12 @@ If you ever need to recreate your database:
     bundle exec rake admin:create
     RAILS_ENV=test bundle exec rake db:drop db:create db:migrate
 
+Configure emails via MailHog (https://github.com/mailhog/MailHog):
+
+    docker run -p 8025:8025 -p 1025:1025 mailhog/mailhog # open http://localhost:8025 to see the emails
+
 Discourse does a lot of stuff async, so it's better to run sidekiq even on development mode:
 
-    mailcatcher # open http://localhost:1080 to see the emails, stop with pkill -f mailcatcher
     bundle exec sidekiq # open http://localhost:3000/sidekiq to see queues
     bundle exec rails server
 
diff --git a/docs/DEVELOPMENT-OSX-NATIVE.md b/docs/DEVELOPMENT-OSX-NATIVE.md
index 1c56df4..c8a0d51 100644
--- a/docs/DEVELOPMENT-OSX-NATIVE.md
+++ b/docs/DEVELOPMENT-OSX-NATIVE.md
@@ -216,7 +216,7 @@ By default, development.rb will attempt to connect locally to send email.
 config.action_mailer.smtp_settings = { address: "localhost", port: 1025 }
 `‍``
 
-Set up [MailCatcher](https://github.com/sj26/mailcatcher) so the app can intercept
+Set up [MailHog](https://github.com/mailhog/MailHog) so the app can intercept
 outbound email and you can verify what is being sent.
 
 ## Additional Image Tooling
diff --git a/docs/TESTING.md b/docs/TESTING.md
index 667873c..fc56522 100644
--- a/docs/TESTING.md
+++ b/docs/TESTING.md
@@ -2,9 +2,9 @@
 
 Some notes about testing Discourse:
 
-## MailCatcher
+## MailHog
 
-Discourse depends heavily on (sending) email for notifications. We use [MailCatcher](https://mailcatcher.me/) 
+Discourse depends heavily on (sending) email for notifications. We use [MailHog](https://github.com/mailhog/MailHog)
 to test emails. It's super convenient!
 
-> MailCatcher runs a super simple SMTP server which catches any message sent to it to display in a web interface. Run mailcatcher, set your favourite app to deliver to smtp://127.0.0.1:1025 instead of your default SMTP server, then check out http://127.0.0.1:1080 to see the mail that's arrived so far.
+> MailHog runs a super simple SMTP server which catches any message sent to it to display in a web interface. Run mailhog, set your favourite app to deliver to smtp://127.0.0.1:1025 instead of your default SMTP server, then check out http://127.0.0.1:8025 to see the mail that's arrived so far.

GitHub sha: fbeb854ffc95f019a89d382b460a6f21efa1c58d

This commit appears in #14500 which was approved by davidtaylorhq. It was merged by techAPJ.