Historical clue formulations

• Base of an encipherment — 2023-08-31
• It might come in a bottle — 2022-07-27
• Text, e.g. — 2014-05-24
• Communiqué — 2007-02-26
• Mail body — 2000-11-25
• Bottle contents, maybe — 2000-11-18
• E-mail — 1999-02-14
• Wire — 1998-02-08
• Bit of E-mail — 1997-11-18
• Bulletin — 1995-01-25
• Phone playback — 1994-11-02