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# The ESP Platform IP can't be used with the MTA

{% hint style="warning" %}
You can't put the IP that's in use by the ESP in velocity-install/conf/ipaddresses
{% endhint %}

This is a very common oversight that will cause Velocity MTA to fail to start because the same ports are required by the ESP and the MTA.

If the MTA and the ESP try to share an IP address, whichever one is started first will block the ports needed by the other one, preventing it from starting.