I see that when mail arrives in the backup mailserver and the primary is still down that it will loop the mail when the mailserver doesn't have a Public IP number

In my case, the backup mailserver has Public IP 193.240.207.200 NATted to x.x.x.200 internally

mail arrives

server tries to deliver to primary 80.242.238.152 but it fails of course

then it sends to public IP nr 193.240.207.200 (it's own public IP on the firewall)

this repeats

I have change IP to public and then it recognizes that it's a local IP

[2019.09.12] 11:59:40.075 [07009] Attempting MxRecord Host Name: 'fallback.soko.nl', preference '20', Ip Count: '1'
[2019.09.12] 11:59:40.075 [07009] The mx record ip '193.240.207.200' is a local ip.  All ip's of a lower preference have been tried.
[2019.09.12] 11:59:40.075 [07009] MxRecord 'fallback.soko.nl' is a localIp, skipping
[2019.09.12] 11:59:40.075 [07010] Attempting MxRecord Host Name: 'fallback.soko.nl', preference '20', Ip Count: '1'
[2019.09.12] 11:59:40.075 [07010] The mx record ip '193.240.207.200' is a local ip.  All ip's of a lower preference have been tried.
[2019.09.12] 11:59:40.075 [07010] MxRecord 'fallback.soko.nl' is a localIp, skipping
[2019.09.12] 11:59:40.075 [07009] Removed from RemoteDeliveryQueue (1 queued or processing)

So Is it possible to add an IP nr manually to the server so It skips because it's locally in case of using NAT