Outlook or Mail Client General Interview Question & Answer
What is Email Servers and Ports
As used by Netwin for brevity the term "email server" refers to the two servers required for sending and receiving email, i.e. the SMTP and POP servers.
Incoming and Outgoing Mail Servers
Incoming Mail Server (POP3, IMAP, HTTP)
The incoming mail server is the server associated with you email address account. There can not be more then one incoming mail server for an email account. In order to access your incoming messages, you need an email client. a program that can retrieve email from an email account, allowing a user to read, forward, delete, and reply to email messages. Depending on your mail server, you can use a dedicated email client (like Outlook Express) or a web browser (like Internet Explorer, For accessing web based email accounts, like Hotmail). The mail is held in storage on the incoming mail server until you download it. Once you have downloaded your mail from the mail server it cannot be downloaded again. In order to download your Email, you must have the correct settings configured in your Email client program. Most incoming mail servers are using one of the following protocols: IMAP, POP3, and HTTP.
Outgoing Mail Server (SMTP)
This is the server used only to send emails (to transport them from your email client program to the receiver). Most outgoing mail servers are using the SMTP protocol (Simple Mail Transfer Protocol) for sending emails. Depending on your network settings, the outgoing mail server can belong to your ISP or to the server where you setup your email account. As an alternative, you can use a subscription based SMTP server (like smtp.com), which will allow you to send emails from any email account you already own. Due to anti-spam reasons, most of outgoing mail servers will not let you send emails if you are not logged on their network. An open-relay server will allow you to use it for sending emails, no matter if you belong to its network group or not, thus it is a heaven for spammers.
For networks, a port means an endpoint to a logical connection. The port number identifies what type of port it is. Here are the default email ports for: -
POP3 - port 110
IMAP - port 143
SMTP - port 25
HTTP - port 80
Secure SMTP (SSMTP) - port 465
Secure IMAP (IMAP4-SSL) - port 585
IMAP4 over SSL (IMAPS) - port 993
Secure POP3 (SSL-POP) - port 995
Email Protocol:-IMAP, POP3, SMTP & HTTP
Basically, a protocol is about a standard method used at each end of a communication channel, in order to properly transmit information. In order to deal with your email you must use a mail client to access a mail server. The mail client and mail server can exchange information with each other using a variety of protocols.
IMAP Protocol: -
IMAP (Internet Message Access Protocol) –Is a standard protocol for accessing e-mail from your local server. IMAP is a client/server protocol in which e-mail is received and held for you by your Internet server. As this requires only a small data transfer this works well even over a slow connection such as a modem. Only if you request to read a specific email message will it be downloaded from the server. You can also create and manipulate folders or mailboxes on the server; delete messages etc. see also IMAP.org
POP3 Protocol: -
The POP (Post Office Protocol 3) protocol provides a simple, standardized way for users to access mailboxes and download messages to their computers. When using the POP protocol all your email messages will be downloaded from the mail server to your local computer. You can choose to leave copies of your emails on the server as well. The advantage is that once your messages are downloaded you can cut the internet connection and read your email at your leisure without incurring further communication costs. On the other hand you might have transferred a lot of message (including spam or viruses) in which you are not at all interested at this point. See also POP3 Description (RFC)
SMTP Protocol: -
The SMTP (Simple Mail Transfer Protocol) protocol is used by the Mail Transfer Agent (MTA) to deliver your Email to the recipient's mail server. The SMTP protocol can only be used to send emails, not to receive them. Depending on your network / ISP settings, you may only be able to use the SMTP protocol under certain conditions (see incoming and outgoing mail servers) see also SMTP RFC
HTTP Protocol: -
The HTTP (Hyper Text Transfer Protocol) is not a protocol dedicated for email communications, but it can be used for accessing your mailbox. Also called web based email, this protocol can be used to compose or retrieve emails from an your account. Hotmail is a good example of using HTTP as an email protocol.