SMTP (Simple Mail Transfer Protocol) is a protocol for sending email messages between servers. A standard SMTP server is a peer to all other internet SMTP mail servers, sending messages via the most direct route available to the recipients’ mail server and receiving messages from other servers. SMTP servers do not "log-in" to retrieve messages, they simply wait for messages to come to them.
POP (Post Office Protocol) is a protocol that allows e-mail client programs (also known as POP clients) to log-in and download messages from the mail server. The user then reads the messages and replies, and the e-mail program uses the SMTP protocol to send the messages back out through the server. APOP (Authenticated Post Office Protocol) uses a secret pass phrase system to identify each client for security.
IMAP (Internet Mail Access Protocol) allows users to read their mail on the server and only download messages and attachments to a local machine when appropriate. Its main advantage is that the user can see all the message headers at a glance, and open only those which are interesting. This saves significant download time, especially if users often forward or delete messages without reading them.
HTML (Hypertext markup language) is the source code read by the web browser. It is an international language representing text, image placement and document linking(hyper-link). You can view the source code of this page by doing the following. MS Explorer: Edit > view > source; Mozilla: View > page source; and Netscape is something similar.
It is an email address that points to your mailbox or a number of mailboxes. It can also be described as a router.
The default setting on all email is 45 days. At which stage you will be notified, via email, and these messages will be put in a folder named Old. We don't measure the amount of activity on email addresses and so an address won't ever expire automatically.
Spam is basically unsolicited email of any kind, usually advertising some product or service. It is illegal and is blamed for slow loading webmail, SMTP issues and mail server crashes.
You may have: forgotten to tick that box on a web form that says "don’t put me on your mailing list"; sent bulk mail without using Blind Carbon Copy (BCC); forwarded on a partition or humorous email that contains lists of other people's addresses.
Unsubscribing? You can unsubscribe from most ligitimate mailing lists. Unsubscibing from other mailing lists, like those that advertise Viagra, money loans and porn, maybe acknowledging that you have an active email address.
Bouncing? Apple's Mail has a great feature called bouncing. It will send a message back to the source saying that there was a fatal error in finding your address and that the mail has been returned. This only works when the sender has a fixed email address.
Spamcop and spam reporting If you are really sick of being hassled by spam, have a look at Spamcop.net and file a report. You will need to register but this is free and they will try and track down the offender. The process in itself might be quite interesting.