Do you get any delivery notification when you send the same email to the same recipient(s) via email clients like Outlook with tracking options enabled?
If not, then most likely the recipient's email server is ignoring Return-Receipt-To header. It's actually quite common for an email server to ignore that header particularly when email is generated from another domain (e.g. Junk emails).
@niharikaT There is no configuration needed for this Niharika.
What i have observed is :
If Pega Email Account rule uses email Test1@abc.com where domain is abc.com, for sending/receiving emails, and the recipient's email address on the other hand [eg. Test4@abc.com ] which will receive email from Test1@abc.com , belongs to same domain [which is abc.com in this case] then you should be good to receive delivery receipt as well.
If the email address has different domain Test4@xyz.comthan the one which Pega sends email (in this case abc.com) , then sender itself generates the relay notification because there could be restrictions on xyz.com to send delivery receipt to email outside domain xyz.com.
So in summary, If your Sender email address and recipient's email address both belong to same domain, it should receive delivery receipt unless there is no explicit restriction on recipient's email to send one.