SMTP Port (25) open

[TheSwiss]

Hi all,

while trying to figure out if my settings on my ac87u are correct,
I did an online port scan, using

http://www.dnstools.ch/port-scanner.html

I was surprised to find the SMTP Port (25) listed as open, even though I have not put an entry anywhere in the Router settings...

Is there a way to block this port? And why is it open in the first place?

As a router newb, this is very confusing to me...

Cheers, enjoy your weekend!

T.S.

 

[RMerlin]

Hi all,

while trying to figure out if my settings on my ac87u are correct,
I did an online port scan, using

http://www.dnstools.ch/port-scanner.html

I was surprised to find the SMTP Port (25) listed as open, even though I have not put an entry anywhere in the Router settings...

Is there a way to block this port? And why is it open in the first place?

As a router newb, this is very confusing to me...

Cheers, enjoy your weekend!

T.S.

There is no port 25 forward in the firmware code. Make sure it's not a UPNP device on your LAN forwarding port 25. Check the list of forwarded ports under System Log.

Also, did the test really report it as open? Testers tend to report three states: open, closed, and stealth (meaning the connection attempt is silently dropped rather than actively rejected).

 

[TheSwiss]

There is no port 25 forward in the firmware code. Make sure it's not a UPNP device on your LAN forwarding port 25. Check the list of forwarded ports under System Log.

Also, did the test really report it as open? Testers tend to report three states: open, closed, and stealth (meaning the connection attempt is silently dropped rather than actively rejected).

A day is a good day when you learn something new!

Thanks to your answer, I learned something about UPNP and port forwarding. However, at the end it turned out that the port scanner I was using returned a wrong result. Non of the other scanners confirmed an open SMTP port, neither did the log entry on the router.

I appreciate your help and all the work you put into this firmware!

Best regards,

T.S.