Email Errors or Options missing

Symptoms:
You got the following error on alert me option.

The virtual server is not configured to send e-mail. For assistance, contact your server administrator.

OR

Navigate to Site Action > Advanced Permissions > Settings > Access Request option is missing.

OR

Navigate to Site Action > People and Groups > New > Add Users , last section which gives you the option to send an email to the user is missing.

Solution ( UI ):
This is because of the reason SMTP server is not configured for the server farm. Contact you server Administrator to fix the SMTP server information

For Complete Farm :
Central Administration > Operations > Outgoing E-mail Settings

For particular web application :
Central Administration > Application Management > Web Application outgoing E-mail Settings

Solution ( Command Line ):
To configure e-mail settings for the entire farm, use the following syntax:

STSADM -o email -outsmtpserver mail.example.com -fromaddress someone@example.com -replytoaddress someone@example.com -codepage 65001

To configure e-mail settings for a specific Web application, use the following syntax:

STSADM -o email -outsmtpserver mail.example.com -fromaddress someone@example.com -replytoaddress someone@example.com -codepage 65001 -url http://server_name