Luigi Auriemma

I was wondering if anyone has whitepapers on smtp servers.

(I can't find any on google)

any public protocol is documented in RFCs:

http://www.ietf.org/rfc/rfc0821.txt

Ok thanks, I'll check it out.

Quick question, what kind of socket would I use for it?

it's a TCP connection so socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

Thanks a bunch

I try connecting to hotmail.com/mx1.hotmail.com on port 25 but I don't get a response.

depends to what you refer, if you mean that you don't receive data from the server at all or after having sent a command.
Then remember that is possible that your IP range could be not allowed to send mails directly to hotmail.com mailboxes, this is an antispam policy used by some blacklists and mail servers.

ah ok, thats probably it because it doesn't connect.

Although I would imagine all it would do is auto forward any email i send to spam.

there is a difference between the mails you send to a smtp server and from it.

As already said, sometimes there are some antispam blacklists which include the range of IP addresses of an ISP dedicated to home users and so they are classified as untrusted.
So if you, from your home connection, try to send a mail directly using the SMTP server of the recipient (that use these blackslists) is possible that you will be kicked.

Different is if you have the same domain of the SMTP server (for example yourname@hotmail.com and you use the MX of hotmail) and want to send a mail to me, in which case there are no problems since you are a trusted user.

Another problem which can happen when people try to send a mail for the first time is the lack of the <> delimiters in the source/recipient mail addresses (mailf from and rcpt to), in fact using yourname@example.com is wrong and you must use <yourname@example.com>