Problem
You attempt to send emails via HMailServer and receive the following error:
SMTP protocol error: 550 Delivery is not allowed to this address.
Cause
Sending emails to the HMailServer from a different host is prevented by default as this could result in spamming.
Solution
Go to settings => advanced => IP Ranges =>Internet
In the Allow deliveries from section check both
- external to local
- external to external
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