For MBS Mortgage Loans MBS Mortgage LoansMortgage Loan purchased by Fannie Mae in exchange for an issued MBS backed by the Mortgage Loan. , either a Third Party MBS Investor Third Party MBS InvestorMBS Investor for an MBS Mortgage Loan that is not the Multifamily Trading Desk. for Lender-Arranged Sales Lender-Arranged SalesMBS sold to the Lender and held on its balance sheet or delivered to a Third Party MBS Investor. , or the Multifamily Trading Desk Multifamily Trading DeskTeam that: purchases and trades Cash Mortgage Loans and MBS Mortgage Loans for Fannie Mae's own account; and can be contacted at (888) 889-1118. .