On the Tools menu, click Accounts.
On the Mail tab, click New.
In the Account Setup Assistant box, type your name. This is the name that users see when they receive messages from you. Click the arrow to advance to the next screen.
In the Your E-mail Address box, type the e-mail address that is provided by your ISP, and then click the arrow to advance to the next screen.
In the Mail Servers dialog box, click POP3 from the My Incoming Mail Server list.
In the Incoming mail server box, type the server name or address for the POP3 server.
In the Outgoing Mail box, type the Simple Mail Transport Protocol (SMTP) server address, and then click the arrow to advance to the next screen.
For more information about either your POP3 or SMTP server name, contact your ISP or administrator.
In the Account ID box, type the account identification that is provided by your ISP or administrator. This account identification can be the part of your e-mail address before the at (@) sign.
In the Password box, type the password that is provided by your ISP or administrator. The Save Password option is automatically selected. If you want a to be prompted for a password when you check messages, click to clear the Save Password check box, and then click the arrow to advance to the next screen.
In the Account Name box, type a descriptive name for the account. This is a display name, and is not an item provided by your ISP or administrator.
Please make sure that setting of your outlook client are as mentioned below :
Username : your email account
password : your password
Incoming & Outgoing mailserver : mail.yourdomainname.com
Outgoing mail SMTP: 25 ( Also you can use 26 )
Incoming mail POP3: 110
“My server require authentication” & “leave a copy of message on server” is checked/enable.
Usually, the port used for the Outgoing Mail Server/SMTP Service is 25. However, there might be a situation where your ISP might be blocking the use of port 25 for SMTP service. Many ISPs block port 25 in order to minimize the amount of spam sent using their network. If you are facing issues sending mails using the default port 25, you can confirm with your ISP whether port 25 is indeed blocked by them.
To circumvent this, Sibername allows you to use an alternate port 26 for sending mails if port 25 is blocked: