On Sunday, TMZ obtained the letter - which was faxed to Bullock's agent - from Smith, herself.
It began, "I'm sure your wondering why I'm writing this letter to you. I felt I needed to reach out to you and tell you how deeply sorry I am for everything that you've been through."
She wrote (proceed with caution, grammar-wise), "I know that this message wills most likely go unanswered, but I want you to know that I am sorry for any hurt or pain that I have caused you," reports TMZ.
Smith continues, "My actions of engaging with a married man are unforgivable."
The alleged mistress also wrote, "I know nothing I can say in this letter is going to make the pain of my actions go away."
TMZ's copy of the letter ends with, "From the bottom of my heart I hope you accept my sincere apology. Please contact me if you wish to discuss on the phone or in person."
The Oscar-winning actress will probably have better things to do.