Why does Debian get "no route to host" when trying to connect to a host on port 80?

Question

linux

"Suddenly" a strange problem appeared, when trying to connect to a host on port 80, "no route to host" falls out. Ping, connection via ssh, via smtp and pop3 works.
The host is debian stable, external IP from WebPlus. I didn't change the settings, everything worked before. For the experiment, I changed the policy in iptables by default to ACCEPT, but nothing has changed (port 80 is open by a separate rule).
I tried to connect from different hosts, everywhere is the same:

[email protected]:/home/sergey# telnet 89.163.xx.xx 25
Trying 89.163.xx.xx...
Connected to 89.163.xx.xx.
Escape character is '^]'.
220 mail.xxxxxxx.spb.ru ESMTP Postfix (Debian/GNU)
quit
221 2.0.0 Bye
Connection closed by foreign host.
[email protected]:/home/sergey# telnet 89.163.xx.xx 110
Trying 89.163.xx.xx...
Connected to 89.163.xx.xx.
Escape character is '^]'.
+OK Dovecot ready.
quit
+OK Logging out
Connection closed by foreign host.
[email protected]:/home/sergey# telnet 89.163.xx.xx 80
Trying 89.163.xx.xx...
telnet: Unable to connect to remote host: Нет маршрута до узла

I looked at the interface with tcpdump, when I try to connect to port 80, nothing comes up.
I can't understand how this is possible? It seemed to me that the route to the host is either there or not, regardless of the protocol.

Answer 1

Perhaps some gateway on the way cuts port 80.
Compare findings traceroute 89.163.xx.xx andtraceroute -T -p 80 89.163.xx.xx

Answer 2

Probably your ISP is naughty. See tcpdump'om what ICMP arrives on the client and from what address.