Connecting to Exchange Server 2003 over POP using openssl s_client

Question

I'm trying to fetch emails programmatically from Exchange 2003 over POP. As a proof of concept I'm trying to connect using openssl s_client.

I've started the POP service on my Exchange server. Trying to connect using

openssl s_client -connect MYEXCHANGESERVER:995

returns

20303:error:140790E5:SSL routines:SSL23_WRITE:ssl handshake failure:s23_lib.c:188:

Trying

openssl s_client -connect MYEXCHANGESERVER:995 -starttls pop3

returns

CONNECTED(00000003)
write:errno=32

[UPDATE] In response to jj33's advice, netcating (originally telneting) onto the server as follows:

nc -v MYEXCHANGESERVER 995

returns

Connection to MYEXCHANGESERVER 995 port [tcp/pop3s] succeeded!

Then the connection automatically closes.

Netcating onto port 110 (insecure pop) returns

+OK Microsoft Exchange Server 2003 POP3 server version 6.5.7638.1 (MYEXCHANGESERVERNAME) ready.

For every command I try I get back

-ERR Protocol error.

[/UPDATE]

Forgive a newb - I'm basically shooting wildly in the dark with no idea on what I'm supposed to be doing. In the past I've read my GMail over openssl s_client, and setting up those certificates was easy and well documented. I would imagine I need to set up some sort of certificate here as well, and I've looked a bit at using a .pfx file. But like I said, I'm completely lost here.

Thankful for any advice,

Andreas

Answer 1

As a troubleshooting step, try connecting directly to 995 w/ telnet and see if it's presenting a plaintext banner. You might either not have encryption at all or you might have it set up to upgrade to encryptiono in the protocol (I would say STARTTLS in SMTP, not sure what the verb is in POP)

Answer 2

Drop the starttls flag -- you're not running TLS over 110, so that flag will break stuff.

Answer 3

I know this was 7 years ago now, but I just found the fix for the same problem. The solution was to pass the -crlf flag to s_client.

openssl s_client -crlf -connect MYEXCHANGESERVER:995

Source: test a pop3 secure ssl port 995