SMTP Overview

SMTP stands for simple mail transfer protocol and is the protocol used for sending email on the Internet. To help in understanding the SMTP email process it is useful to compare the sending and receiving of email with the sending and receiving of normal mail.

To send normal mail you simply go to any post box and drop in your letter. To send email on the Internet you connect your email to any SMTP server and send your email. The SMTP server can belong to anyone and doesn't need to be the same as your normal email provider.

This was the case until the system was abused and innocent ISPs were used for sending SPAM. Today almost all SMTP servers only allow you to send email through them if you are using either a trusted IP address (one they themselves allocated) or first authenticate yourself (login).

There are two ways email providers authenticate an SMTP user.

IP address
Login

IP address

When you connect to your ISP you are allocated and IP address. If your email account is held by your ISP then you normally don't need to authenticate to send email. This is because the ISP detects that the sending SMTP client has a known IP address and hence trusts it.

Accessing Your email Using a different IP address than Normal

This scenario is typical when you have a dial up or broadband account and you are able to send email normally from home but when you visit another office and connect to their Network you find that you are able to receive email ok but not send email.

This is because the email provider as detected that you are using an IP address that is not trusted and hence thinks you are trying to spam. The usual solution is to configure SMTP authentication as detailed below.

Login or SMTP Authentication

If your ISP isn't your email provider then you normally need to login in order to send email. This is configured in Outlook Express as detailed below:

From the Tools menu, choose Accounts.

Select the Mail tab.

Click the account to highlight it.

Click the properties button

Select the Servers tab.

outlook-express-advanced-smtp-configuration-1

Check the box next to My Server Requires Authentication.

Usually you logon using the same account as for POP3 email. If so then you have finished configuration. However you may be sending mail using a different provider than for receiving email. This happens often when moving ISPs. If this is the case you will need to click settings tab and then select the logon using radio button and enter a username and password.

outlook-express-advanced-smtp-configuration-1

Click OK.

ISPs and Web Portals

An ISP (internet service provider) provides physical dialup or broadband connection to the Internet. ISP also generally provide other web services like email accounts and web space. e.g.. BT, Cable and Wireless.

A Web portal doesn't provide Internet access but Internet services like email, web hosting e.g. Yahoo. To use these you need first to connect to the Internet using an ISP.

Some providers actually provide both e.g. AOL.

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SMTP Overview