Mushroom Networks Documentation

SMTP failover

SMTP failover would require both the outgoing and incoming configuration.

Outgoing

Set the Reverse DNS with multiple IPs (WAN1, WAN2, etc) pointing to the same domain

Incoming

Following example taken from this article:

You can specify MX records for a single Internet domain — for example, acme.com — with a single Internet domain name, such as acme.com. Use the server’s fully-qualified Internet host name in the MX and A records — for example, mail1.acme.com.

For example, configure a backup SMTP server (mail2.acme.com) to deliver or forward mail when the primary SMTP server (mail1.acme.com) is unavailable:

    1. MX record: acme.com IN MX 5 mail1.acme.com

A record: mail1.acme.com IN A 192.168.10.17

    1. MX record: acme.com IN MX 10 mail2.acme.com

A record: mail2.acme.com IN A 192.168.10.18

Messages addressed to acme.com route to mail1.acme.com first because the record’s preference (5) is lower. If mail1.acme.com is unavailable, mail is routed to mail2.acme.com.

© 2026 Mushroom Networks Inc. All rights reserved.

Contact Sales