Debug Mode Only Works Sending Email In C#?

i wrote a sending email function that only works on my debug mode(debug local server) when i publishing and hosting C# code that function doesn't work. This is my email configuration function

<configuration>
<system.net>
<mailSettings>
<smtp from="admin@XXXX.com">
<network host="smtp.XXXXX.com" port="25"
userName="admin@XXXXX.com" password="XXXXX" />
</smtp>
</mailSettings>
</system.net>
<appSettings/>
<connectionStrings/>
<system.web>