CAS uses the SMTP server provided by Mailgun to send email messages to you & your customers. There are several reasons why outbound messages may fail to send. These are the most common causes.

First, identify if you can connect to Mailgun:

nc smtp.mailgun.org 587

• You should see the netcat utility connect “220 Mailgun Influx ready”:

• If connected, press CTRL+C to exit netcat.

If it doesn’t connect, then your outgoing port 587 is blocked.

1. Your firewall may be blocking outbound port 587 traffic, see: Configuring Server Firewalls

2. Digital Ocean has blocked your outbound mail traffic. Contact Digital Ocean. Make sure that you mention your use case, and that you are a GB Operator. Speak to a live human about it.

3. Your server IP may be on a blacklist. Contact Mailgun.

If you have tried these steps and cannot resolve the problem, contact support.