undelivered email
I replied to an old email and the senders address at 3:05pm.
I just received an undeliverable notification at 6:14pm.
Why did it take over 3 hours to let me know my email was not received?
I understand there are several attempts but this is, in my opinion way too long for anyone to wait before knowing the information sent was not received. Is there a setting that can change this or fix this? Thanks

Delivery records in the full headers show when each computer received the message. The first delivery is at the bottom; the newest at the top. If you find a large time gap between delivery records, that shows which computer delayed before sending it to the next computer. https://help.yahoo.com/kb/SLN22026.html