Hi @Priyanga_Karnan ,
1)First pass the mail message to the queue by using add queue item activity and changing the type to System.net.mail.mailmessages.
2)Secondly, just provide the queue name which you used to add mail message in get transaction item.
3)In out_transaction_item you will get the queue item which consists the mail message.
4)Now in process transaction perform whatever desired operation you want to perform with the mail message.
Thanks & Regards,
Shubham Dutta