The Department of the Outside is a government agency of the Tzenkethi Coalition responsible for dealings with foreign powers.
In 2383, Starfleet Intelligence was able to have Alex Gardner infiltrate the Department of the Outside disguised as a Tzenkethi, as was the Cardassian Intelligence Bureau, who embedded Neta Efheny in the department. Gardner approached Efheny for exfiltration when the Tzenkethi were close to discovering him, although Efheny killed Gardner when he threatened her friend Corazame. Efheny remained behind on Ab-Tzenketh, while Corazame brought the information that Efheny had gathered from the Department of the Outside to the Cardassians. (ST - Typhon Pact novel: Brinkmanship)
During her time as a cleaner in the offices of the Department of the Outside, Corazame found she often listened to the conversations of her superiors. This valuable information brought her to the attention of Peter Alden and Starfleet Intelligence after her departure from Ab-Tzenketh. (DS9 novel: The Missing)