Add contributed protonmail settings

Thanks to @marc_remmen.io

Closes #8079

Changelog: Added
Signed-off-by: Jason Young <[email protected]>

Author: Jason Young

doc/settings/smtp.md

@@ -1294,6 +1294,23 @@ gitlab_rails['smtp_authentication'] = "plain"
 gitlab_rails['smtp_enable_starttls_auto'] = true
 ```
 
+### Proton Mail
+
+Proton documentation: [How to set up SMTP to use business applications or devices with Proton Mail](https://proton.me/support/smtp-submission)
+
+```ruby
+gitlab_rails['smtp_enable'] = true
+gitlab_rails['smtp_address'] = "smtp.protonmail.ch"
+gitlab_rails['smtp_port'] = 587
+gitlab_rails['smtp_authentication'] = "plain"
+gitlab_rails['smtp_enable_starttls_auto'] = true
+gitlab_rails['smtp_user_name'] = "<the Proton email address for which you generated the SMTP token>"
+gitlab_rails['smtp_password'] = "<the generated SMTP token>"
+gitlab_rails['smtp_domain'] = "<your domain>"
+gitlab_rails['gitlab_email_from'] = "<the Proton email address for which you generated the SMTP token>"
+gitlab_rails['gitlab_email_reply_to'] = "<the Proton email address for which you generated the SMTP token>"
+```
+
 ### More examples are welcome
 
 If you have figured out an example configuration yourself please send a Merge