Cannot connect via IMAP over LAN, works when connecting over WAN

So as the title states, I cannot make an IMAP connection when I am on my LAN. As soon as I am connecting to my WAN address it will connect. Same configuration and everything. I’ll have nothing on my WiFi but if I access it over my phone’s data it will connect fine.
For some context I am running a few things on my server that I access from outside my LAN (nextcloud, paperless, photoprism, etc). and they are all running behind a reverse proxy using Nginx Proxy Manager, mailcow included. I actually had this same problem with everything else I am hosting because my router doesn’t support NAT loopback and I fixed it by running a custom dns server on a pihole with dns records for everything I’m hosting.
And to make it a little more interesting I can access mailcow’s webui from my LAN including SOGo. It is just IMAP that is not working.