POP3 connection drops, but why?

RouterOS Beginner Basics
1

Hi,

My setup worked for 2 years, but approx. 2 weeks ago, POP3 fetch from an external server stopped working. I am not so into this NAT/firewall stuff, I just used the basic setup.
If I use torch, I think I can see that there is a reply from the server but it’s stuck at the router WAN interface

[admin@MikroTik-Verteiler] > /tool torch interface=ether1 port=995 duration=30s
SRC-PORT                          DST-PORT                                  TX         RX TX-PACKETS RX-PACKETS
995 (pop3s)                       44458                                 592bps       0bps          1          0
                                                                        592bps       0bps          1          0

Is this correct? Where can I get further informations, why this is stuck?

[edit] I just found out that also ssh on port 22 is not working.

Many thanks for any hints,
Christof

2

you are convinced that nothing has changed +
no one has changed the router configuration +
no one has updated the operating system +
no one has updated the mail program +
no one has updated the mail server +
various and possible like the previous ones =
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
ask your ISP

3

Of course I asked the ISP, but they are not very responsive and just says “ask the POP3 provider” which is even not answering (gmx.net) :frowning:

So I would like to check where it is blocked. If I look with tools/torch, I see that there is traffic on ether1 (where the ISP modem is attached) on TX but not on RX on port 995. What does this tell me?

[admin@MikroTik-Verteiler] > /tool torch interface=ether1 port=995 duration=30s     
SRC-PORT                          DST-PORT                                  TX         RX TX-PACKETS RX-PACKETS
995 (pop3s)                       50284                                 592bps       0bps          1          0
                                                                        592bps       0bps          1          0

Maybe you can give me a hint…

4

Run tcptraceroute against POP server and correct port and see how far it gets.

Yes, it’s important to run traceroute in TCP mode (not every traceroute tool can do it) to avoid tripping on selective firewalls.