Since I wrote up testing pop3 with telnet, I thought I would also write about how you can test SMTP with telnet.
From a command line in windows:
telnet
open IPofSmtpServer 25
220 mail.server.domain Microsoft ESMTP MAIL Service, Version: 6.0.3790.3959 ready at . . . .
ehlo test.com
(test.com is the FROM domain)
250 OK
mail from:me@myDomain.com
250 2.1.0 me@myDomain.com. . . .Sender OK
rcpt to:you@yourDomain.com
250 OK – you@yourDomain.com
DATA
354 Start mail input; end with <CRLF>.<CRLF>
Subject: The Subject of the message.
Press enter TWICE.
The body of the message goes here.
Press enter.
Enter a single period (.) and press enter once more.
250 2.6.0 <………………….> Queued mail for delivery
Quit
221 2.0.0 mail.yourDomain.com Service closing transmission channel