Hello, I'm trying to connect to an SMTP server using telnet via putty. Not just well known domains such as bigstring, aol, gmail, hotmail etc but also endless amount of not known or not popular ones. The problem is that although nmap says that port 25 is open, I can not establish any connection to ANY SMTP server (it just timeouts). Does anybody know a possible cause for this? I have tried disabling my firewall and using a proxy, but it still doesn't connect and now I've ran out of ideas. I also tried to disable my avast as well as legally used ip switcher program to make sure the problem is totally independent from my ISP. Its very important for me to get the solution to this, even if there might not be one. I have to do something to fix this problem and hopefully someone could help.

been waiting for a while now, anyone knows the solution?

Do you really mean _any_ smtp server? What about your own ISP's. Maybe they block smtp unless to their own servers or unless coming from certain blocks, etc.

Try smtp.live.com on 25 then on 587.

Are you remembering to tell putty '25' ?

Lots of SMTP servers use reverse name lookups for validation, and if there is not reverse DNS, they don't allow the connection.
do you have internet resolvable forward and reverse A, and PTR records for your public ip address?

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timhalo yes i tried, also via putty as well as telnet and cmd but it always timeouts - any smtp server. I am able to send email messages fine, no matter if i send to @gmail.com or @aol.com or @bigstring.com or @totallyunknownword.com etc.

ristau I apologize but I don't understand your question?

I believe what ristau is saying is re: https://en.wikipedia.org/wiki/Forward_C ... everse_DNS .

There's at least one mail server you can telnet to on it's listening port, since you can send email fine.

Why you can't hit MS's mail server on either 25 or 587 that's curious. I was leaning towards intentional blocking because of the timeouts; either a f/w on your host, edge-router, or your isp. I dunno. I can get to mail servers just fine, e.g. below....but of course after opening my own fw's.

so how do i fix the problem?

Contact your ISP....see if they really are filtering smtp. If so, negotiate.
Also whoever, you or your isp, is hosting the forward & reverse zones can fix/create the A & PTR records.