Очень просто:Вот тут все ОК
++++++++++++++++++++++++++++++++++++++++++++
[roman@roman ~]$ telnet 194.67.23.102 110
Trying 194.67.23.102...
Connected to pop.mail.ru (194.67.23.102).
Escape character is '^]'.
+OK
^]
telnet> quit
Connection closed.
++++++++++++++++++++++++++++++++++++++++++++
А вот тут - таймаут:
++++++++++++++++++++++++++++++++++++++++++++
[roman@roman ~]$ telnet 194.67.23.102 25
Trying 194.67.23.102...
[roman@roman ~]$
++++++++++++++++++++++++++++++++++++++++++++
++++++++++++++++++++++++++++++++++++++++++++
[roman@roman ~]$ host 194.67.23.102
102.23.67.194.in-addr.arpa domain name pointer pop.mail.ru.
[roman@roman ~]$ host smtp.mail.ru
smtp.mail.ru has address 194.67.23.111
[roman@roman ~]$ telnet 194.67.23.111 25
Trying 194.67.23.111...
Connected to smtp.mail.ru (194.67.23.111).
Escape character is '^]'.
^]
telnet> quit
Connection closed.
[roman@roman ~]$
++++++++++++++++++++++++++++++++++++++++++++
Все ОК.