Just another point on the OP's side for a claim....isn't it a felony to tamper with someone's mailbox? Legally, I don't think you are allowed to put anything in, or take anything out of someone else's mailbox unless you are a postal employee....here - I found this....(woops - edited to say I meant crime, not felony - lol) At any rate - she could pay you what that cake was worth instead of spending the $ on a postal fine??
18 U.S.C. 1725 states:
"Whoever knowingly and willfully deposits any mailable matter such as
statements of accounts, circulars, sale bills, or other like matter,
on which no postage has been paid, in any letter box established,
approved, or accepted by the Postal Service for the receipt or
delivery of mail matter on any mail route with intent to avoid payment
of lawful postage thereon, shall for each such offense be fined under
this title"
"TITLE 18 > PART I > CHAPTER 83 > Sec. 1725"
Legal Information Institute
http://answers.google.com/answers/threadview?id=288629
It appears that violation of this provision is an infraction, carrying
a fine of not more than $5,000 for an individual, or not more than
$10,000 for an organization.
"TITLE 18 > PART II > CHAPTER 227 > SUBCHAPTER A > Sec. 3559"
[defining "infraction" in subsection (a)(9)]
Legal Information Institute
http://www4.law.cornell.edu/uscode/18/3559.html
"TITLE 18 > PART II > CHAPTER 227 > SUBCHAPTER C > Sec. 3571"
[establishing fines for an infraction in subsections (b)(7) and (c)(7)]
Legal Information Institute
http://www4.law.cornell.edu/uscode/18/3571.html
See also:
"Domestic Mail Manual - D041 Customer Mail Receptacles" [especially section 1.3]
United States Postal Service
http://pe.usps.gov/cpim/ftp/manuals/dmm/D041.pdf