How Much Do You Know About Email? Quiz

Answer: Simple Mail Transport Protocol

SMTP, or Simple Mail Transport Protocol, is the standard used to communicate with remote servers via email. The protocol was first defined in 1982. While others exist, SMTP has become the accepted standard to provide global communication.

Answer: A published record that indicates servers authorized to send email

SPF is a record published in DNS (Domain Name Servers) that defines the server(s) authorized to send email from a given domain. SPF can be used as a tool to help prevent email spoofing. While SPF is very effective when used as designed, it has not gained wide acceptance.

Answer: A DNS record that indicates a server that is available to receive incoming email

MX is a record published in DNS (Domain Name Servers) which tells remote systems to what servers they should send email addressed to a given domain. Multiple records may be published with different costs, or priorities, in order to provide alternate routes in the event a server is unavailable.

These can be the same servers which receive inbound email, but those roles are frequently separated.

Answer: Everything worked and your email was delivered

The SMTP code 250 is the normal conclusion of a successful email transmission. This does not, however, guarantee that the message was delivered to the intended recipient. This code only confirms that the message was delivered to the next hop. Some email systems have complicated routing which results in relay through several hops before being delivered to the recipient mailbox.

Answer: 25

Although it is possible with most email systems to use other ports, the standard for SMTP (Simple Mail Transport Protocol) is port 25. This is generally only changed for internal email systems or to support encryption. Port 80 is the standard for HTTP, or internet browsing. Port 389 is used for Lightweight Directory Access Protocol, or LDAP. Port 20 is used for FTP, File Transport Protocol.

Answer: Envelope, Header, and Message Body

The message envelope contains information used by the server to accept or reject a message. This prevents the need for a server that may be processing millions of messages per day to examine the full email for every transaction. This is the part of the email which contains the true sender and recipient information.

The email header contains routing information and to and from details. However, it is possible for a spammer to forge some of the header information and make the message appear to be from a different sender.

The message body is what is displayed to the recipient when opening the email.

Answer: Multipurpose Internet Mail Extensions

Multipurpose Internet Message Extensions, or MIME, defines standards for formatting non-ASCII (American Standard Code for Information Interchange) content over the internet. This is the functionality which allows sending things like Microsoft Office or Adobe files, image or video files or audio files as attachments to email messages. MIME standards were first defined in 1992. S/MIME, or secure MIME, is used for encrypted email.

When an internet email is sent, the content is converted to a MIME format while in transit.

This often results in an increase in size which can cause confusion when dealing with email size limits. On receipt the email content is converted back to its native format.

Answer: The sender crafts a message header to make an email appear to come from a trusted sender

Email spoofing is used in attempts to make the email recipient believe that the message was sent by someone other than the actual sender. This is done either to hide the true sender or enhance credibility by appearing to be from a known or trusted source. Emails can be crafted in a manner that makes the friendly from line displayed in the email completely different from the actual sender.

Answer: Exchange

Microsoft Exchange Server is a client-server mail system which is integrated with Microsoft Active Directory on Windows networks. Exchange provides real-time database replication to provide redundancy through Database Availability Groups. Exchange email services can be through on premise installations, managed service agreements, or fully cloud based.

Answer: RCPT TO

Email transmission always starts with an EHLO (or HELO) server identification command. Following that a standard transaction will include MAIL FROM to indicate the sender, RCPT TO in order to indicate the intended recipient(s), DATA to include message text, and will end with a period to mark the end of the email transmission. QUIT is used to close the connection.

Other commands that may be used, or that are technically not true SMTP commands include SIZE, Subject, CC, and Reply-To. This sequence illustrates just how easy it is to spoof email addresses.

It is only a matter of typing the fake address after the MAIL FROM command. It is really as easy as writing a fake return address on a standard mail envelope. This is the security issue Sender Policy Framework, SPF, was intended to address.