There are a few other similar questions on Splunk answers, but each answer has been tailored to each asker's use case. I'm obviously also looking to get it answered for my use case, but I'd prefer answers that are also more broadly applicable to the community.
I have an exchange-based alert set up that looks for suspicious emails every three minutes and sends out an alert if one is found with the fields "sender message_subject recipient". I want to add a "seen_count" field that has a count of how many times we've seen that sender over all-time. Basically, I want to be able to do:
Since you can't pass values into a subsearch, how do I do this elegantly? I could count ALL my exchange senders and then left join with that, or create daily reports that update an aggregate sender_count.csv file every day, but neither of those solutions are elegant.