What does this mean ?
I really can't get it
You probably weren't using a custom service, it was just using the built-in local emailer. Like I said earlier, it is most likely spam filters which are catching your emails, as the local emailer has no trust factor.
I guess you are right.
What are you trying to accomplish?
Ans. I want customers should get verification email once they register on website after clicking on which they can post their topic.
What do you expect the Custom Service setting to do?
Ans : I got your point of custom service . If i use gmail service . Then how can i get my the credentials for a Gmail account in the respective fields
Those values are something you get from the provider of the custom email service. The custom service feature is so you can use services that aren't in the list.
I got your point .
Thing is my customers were getting verification mail from my website.
This problem arises in last 5 days.
I use hostgator for my server setup .
how can i know which custom service I was using ?