If you are confused about Keychat changing the sending and receiving addresses for almost every message after reading the note below, let me give you a real-life example. 

Suppose Alice is traveling in the UK and Bob in France. They each stay in a new hotel in a new location every day. They agree to write each other a letter daily, sharing their travel experiences. They only need to inform each other in the letter where they will be staying the next day, and they can successfully send and receive letters. The receiving address is used only once. nostr:note10aym80w2h0f2jda4fw59prerlpch8z7j9l526xzja8xcx5zku7qsxf5qvd 

 What if Bob for some reason misses the message with new address of Alice? 

 Bob will send letter to Alice’s old address. 

Alice will still listen to several old addresses in case. 

 Understood