I am using Google email in Magento,
The customer receiving order confirmation email in spam.
help me to resolve it.
thanks in advance
the best way is to get few of those emails and check the headers - normally, you can see the reason it got into spam in there. the most common would be failed SPF check.
Try to add this SPF record to your domain's DNS:
v=spf1 include:_spf.google.com ~all
I hope this helps.