Hello, welcome, and thank you for choosing Just Answer.
If you just paid the $291 from 2008-2009 online, it could be that they had not rec'd the payment prior to sending the letter out to you. It could just be another demand for payment letter for the $291. On the other hand, it could for something else. You can always call the IRS prior to signing for the letter to see what it is about. 1-800-829-1040. Please note that certified mail from the IRS does not always translate into being an audit notice.
For clarification purposes, note that cash deposits are reported over $10K, you did write that you deposited a check, correct? Even though it was a check deposit, the letter you rec'd may very well have something to do with the deposit since it is out of your normal scope of deposit amounts. Again, if you don't want to sign for the letter, give the IRS a call and ask them about your account. When you call them you don't even have to mention the letter.
You are welcome. You could probably check with the bank to see if they reported the deposit as cash or not since they did not put a hold on it. Regarding your vacation...I agree, not having negative energy in your space is a good thing. Enjoy.