Hi power,

Refer the below article.

How to send email with attachment in ASP.Net

For Gmail:

For gmail below is the smtp.Host and smtp.Port

C#

smtp.Host = "smtp.gmail.com";
smtp.Port = 587;

VB.Net

smtp.Host = "smtp.gmail.com"
smtp.Port = 587

For Yahoomail:

For yahoomail below is the smtp.Host and smtp.Port

C#

smtpClient.Host = "smtp.yahoo.com"; // or smtp.mail.yahoo.com
smtpClient.Port = 465; //or 995

VB.Net

smtp.Host = "smtp.yahoo.com" ' or smtp.mail.yahoo.com
smtp.Port = 465 ' or 995

For Hotmail:

For hotmail below is the smtp.Host and smtp.Port

C#

smtp.Host = "smtp.live.com";
smtp.Port = 25;

VB.Net

smtp.Host = "smtp.live.com"
smtp.Port = 25