Knowledgebase: E-Mail Services
What is an overview of SMTP service?
Posted by Roy Petersen on Feb-15-2007 12:16 PM

The ability to provide E-mail services to clients includes two critical functions: SMTP and POP3. Together, they provide the means for clients to send outgoing mail and check for new incoming mail, respectively.

SMTP service is the side of e-mail that allows clients to send outgoing e-mail messages to any valid e-mail address. The SMTP server performs two basic but important functions. First, it verifies that anyone attempting to send outgoing e-mail through the SMTP server has the right to do so. Secondly, it sends the outgoing mail and if undeliverable, sends the message back to the sender.

Think of the SMTP server in terms of your local post office. Just like snail mail, e-mail is routed in a similar fashion. While it does not cost a client 32 cents to send an e-mail, they must have permission to sent the outgoing e-mail message. The post office requires postage to send the message to the recipient. Woollybear.com requires that you have checked one of your POP3 accounts in the last 30 minutes for new e-mail before being allowed to send. Think of checking before sending the same as buying a stamp at the post office.

Once this requirement is met the mail is sent to the recipient. However, problems can occur both in the delivery of e-mail and postal mail. Mail is sent to addresses which do not exist, and are therefore returned "address unknown" or "user unknown". Just like the postal service returning your mail with a message "stamped" on it as to why it was not deliverable, so will our SMTP server. When e-mail "bounces", or is returned to you, it is done so because it was undeliverable for one reason or another.

Finally, you need to configure your e-mail client so that it knows what SMTP server to use for sending outgoing e-mail messages. In order to send mail through the proper SMTP server, configure your e-mail client to access the SMTP (Outgoing Mail) Server: mail.yourdomain.com.