My Private Space app sends e-mails to an external SMTP server at port 25 rather than using a Heroku add-on. It seems that the app is intermittently having difficulty in sending e-mails.
You will likely see TCP connection errors in your logs. If you are using Rails ActionMailer you will see a slightly cryptic
Net::OpenTimeout·execution expired error in your logs and emails will not be sent.
Our infrastructure provider applies a throttle on egress network connections to port 25 by default on Private Spaces. To work around this, please:
- Use an alternative port to send e-mails. For example, Mandrill also supports ports 587 and 2525; or
- Contact Heroku Support with the name of the Private Space or the app to have the throttle removed for the Private Space
This throttle doesn't apply to Common Runtime apps.