How Email Works

Mail Incoming to Mines.edu

What happens when John Doe at Company (jdoe@company.com) sends email to Susan Tudent (student@mines.edu) at Mines?

John clicks the "send" button after composing his email to Susan, which transfers it from his computer to his company's outgoing SMTP email server. In the above example, it is smtp.company.com.
The smtp.company.com server locates the Mines server, in this case the CSM AC&N Spam Filter server, and transfers the message to mines.edu.
The AC&N Spam Filter server scans the email for spam and virus content. Depending on differing criteria, the email may be tagged or block.
The email is then sent to smtp.mines.edu, which direct the message to the “awaiting delivery” queue:

If Susan's email INBOX size is over quota, the message will be rejected and sent back to smtp.company.com. From there, it will be returned to John with a notice that mines.edu could not deliver the message because the user is over quota.
Presuming the message is delivered, Susan will read it directly by logging on to CSM Webmail or she will POP or IMAP (depending on her email client and settings) directly to her machine to be read and managed from there.

Outgoing Mail from Mines.edu

A similar process occurs when Susan responds to John:

When Susan clicks "send" her email is transferred to Mines outgoing email server, smtp.mines.edu
The email is scanned for virus content and, if no virus is found, forwarded on the smtp.company.com. If a virus is found, the message is quarantined and a warning email is sent in it's place.
When smtp.company.com receives the email, it may be scanned again for spam or virus content, depending on company.com's policies and procedures.
John will log on to his company email to POP, IMAP, read and manage his email.

Scanning Email for Viruses and Spam

The diagram shows what happens to email once it is received by the AC&N email server:

All email received by CSM mail servers is scanned for spam and virus content.
Distributers of known virus or spam content may be blocked from sending email to @mines.edu address without warning.
The email message is analyzed to determine, based on a set of global rules defined by AC&N, is likely to be spam.

Some rules may be modified by users who have enabled the Quarantine Inbox option in their Spam Filter account. More information is available on the Spam Management Services page.
The message is rejected, tagged, quarantined or delivered, depending on rules and including whitelisting, blacklisting and spam scoring levels.
If the email content is seen, based on user enabled Quarantine options, as having a high probability of being spam the message is quarantined.

If the e-mail has a medium probability of being spam, the subject line is tagged.

The email is returned to smtp.mines.edu for processing.
The message is scanned a second time for virus content using a different scanning engine. This provides redundant layers of protection against newly discovered virus content. If the message contains a known virus, fragmented message or incorrectly encoded file, it is quarantined and a warning is sent to the recipient in place of the message.
The message is queued for deliver and delivered to the users inbox.