Conn. Gen. Stat. § 9-139: Outer envelope for return of ballot.

The inner envelope, in which the absentee ballot has been inserted by the absentee ballot applicant, shall be returned to the municipal clerk in an outer envelope endorsed on the outside with the words: “OFFICIAL ABSENTEE BALLOT”. The outer envelope shall also contain (1) blank spaces for the name and return address of the sender and spaces upon which the municipal clerk, before issuance of the ballot and envelopes, shall insert the applicant's name, voting residence by street and number, voting district, the date of the primary, election or referendum at which the ballot is to be cast and, if the absentee ballot is to be cast at a primary, the name of the party holding the primary and (2) a notice, sufficient to warn any person handling the ballot, of the restrictions set forth in section 9-140b concerning who may possess or return the ballot and the restrictions and penalties set forth in section 9-359 concerning the completion or execution of absentee ballots. The clerk shall also inscribe his official address for the return of the ballot on the outer envelope prior to issuance of the ballot and envelopes. All outer envelopes shall be serially numbered.