History of AR Customer Statements

Summary: Wondering if there is a history of statements a customer receives

Content (required): We have this question/scenario. For 5 months we send customers statements with no payment, so now we start sending dunning letters. The customer comes back and says we never sent them statements. How can you prove you sent the statements, is there a history of this somewhere?

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):