Is there a trick to forwarding port 80?

[ParticleBeam]

I'm trying to route port 80 from outside my network to a reverse proxy inside my network.

I have the port forwarding rule set to: Destined Local:True, Destination Port:80
It's forwarded to port 80 of the reverse proxy's IP.

This works perfectly from *inside* my network, but is unreachable from outside.

I realize Untangle reserves port 80 for its own services by default, I've changed the HTTP port it uses.
I'm only using HTTPS to connect to Untangle's admin features anyway.

If I change the rule's Destination Port to something other than 80, it works from outside (but only with the port specified).
What am I doing wrong? Why is port 80 not being forwarded?

If anyone can point me in the right direction, I'd appreciate it.

[jcoffin]

You will need to move the service ports from 80. As 80 is reserved for the GUI. This will change the port of the admin GUI.

Config -> Network -> Services. All the reserve ports are listed at the bottom of the port forwards page.

[ParticleBeam]

Thank you, jcoffin, but I've already done that.

I've moved the service port from 80 to 84, but port 80 is still not forwarding as expected.

[dwasserman]

2 rules only:
Destination address =your public ip address (if is fixed) or any wan (if dinamic ip address)
Destination port =80
Delete "destined local"
Advice: enable threat prevention or your proxy will have a short lifespan

[ParticleBeam]

Thank you dwasserman. I do have a dynamic IP, but there's not an option for a Destination Interface. See image below.
I did try my current public IP as the Destination Address, but port 80 was still not forwarding.

I don't think I'm too far off using the rules: Destined Local:True and Destination Port:80. I've used a similar set successfully for other port forwards.
In fact, when I forward port 81, it works from outside my network. -- When I change it to 80, it doesn't.

It blows my mind that port 80 is so difficult to forward. -- Hopefully someone can tell me what I'm missing.

[ParticleBeam]

I think I know why forwarding port 80 isn't working. -- It actually is, but my ISP is blocking it.
I feel like an idiot. :P

Thank you both for your help and suggestions.

[gravenscroft]

ISPs gonna ISP. Glad you found the problem!