Is there any approach to stop the auto reply e-mail (User has set up OOO message

Please be more specific about the auto-reply e-mail. Are you referring to the alerts notifications? Please review the following documentation: forum.appian.com/.../Configuring_Notifications.html

I am assuming you are sending an email from a process instance and using a receive message listener to pick up the response and want to handle the OOO reply? If so you should be able to capture the email subject and use a function such as search() to look for "Automatic" (or whatever you email server uses) in the value, if found use a decision gateway to loop back to start a new instance of the receive message listener to negate the OOO response.

We dont want to recieve any message from the user.
We have an email node which sends email to set of users in a group and lets say if one user of that group has set up OOO message, simply auto reply. His OOO message triggers as soon as he receives an email from Appian, then he gets an undelivered email which user doesnt like to see. So what is the possible approach for receiving auto emails?

Thanks!

That is something the user has to configure at the email client level since it's the mail client kicking off the OOB email, Appian is not involved in this process at all.

Some email clients have an option to indicate whom should receive the OOB email.