tax problems didn't file three years

2006, 2007, 2008. I had some kind of depression and ....
I have some rental properties. I didn't worked for two years except rental income, my hu*****and works as an engineer.
Today, one of the tenants sent me an email said IRS went to her house and told her soon my property will be frozen.
I did receive IRS letters but didn't open it.
Is this sounds right? what should I do?
Please help, I really appreciated your help.