@neerajrtiwari I usually start by asking whomever sets up most emails/scripts/workflows in the account since that can be the quickest option. But if that person isn't at your company or something anymore, you could try downloading all script files from your file cabinet and doing a search of all files for "nlapisendemail" or "email.send", which would show you if there's a script sending them. Checking workflows would probably be easiest manually, so long as you don't have a ton of them. You can limit that by looking only at workflows related to the records that the emails are about (e.g. if it's an email about sales orders, it would likely be a workflow on either transactions or customer records). On saved searches, you likely also want to check for searches where there's an individual recipient and not just recipient from results. You can do a search of all saved searches which send any emails by filtering to "triggered" = "T" OR "scheduled" = "T"

It would have been so much easier if we had a way to do a saved search on searches where we can put a criteria on email subject.

I agree, there are a lot of things lacking in the saved search searches IMO - would like to be able to search for searches which use a certain field in a filter or column too.