Problem with sending mail in NIFI

[#1]

Hi, I have the following problem, I have a flow that uses the Mergerecord processor at some point, generally I have about 5,000 records at the input and I need to merge them. Generally, it works ok, but sometimes somewhere along the way one or two records fall out and I get an error when merging that it cannot be merge because the quantity is not correct. This is also ok, but in such a situation I would like to receive an e-mail with information about the error in the merg. How can I make this e-mail come only once and not as many times as I have records in my flow? I've been struggling with this for the second day now and for now I receive an e-mail notification as many times as I have records that have not been merged.Maybe someone know how can I solve this problem?

[#2]

@MWM Before sendEmail you need to add a DetectDuplicate processor.   

https://nifi.apache.org/docs/nifi-docs/components/org.apache.nifi/nifi-standard-nar/1.12.1/org.apach...

You can find a sample template here:

https://github.com/steven-matison/NiFi-Templates/blob/master/DetectDuplicate_DistributedMapCache_Dem...