This episode confirms that T'Pol is not the first Vulcan to serve on a Human starship. Phlox does, however, mention that T'Pol is at that point the longest-serving one.
This is, chronologically, the first mention of Coridan and its people. As established in Journey to Babel (1967) and Sarek (1990), Coridan was (presumably) admitted into the Federation at the Babel Conference in 2268, with Vulcan voting in favor of admission. It was also noted in "Babel" that Vulcan had no mining interest on Coridan.
In the teaser, it is revealed that Captain Gardner was considered the most suitable choice to captain Enterprise by Ambassador Soval. However, Admiral Maxwell Forrest ultimately narrowed down the candidates for the captaincy to Jonathan Archer and A.G. Robinson instead, revealed in First Flight (2003), pointing out that the Vulcan High Command was not in charge of Starfleet's personnel assignments.
The teaser marks the end of the joint fleet operations between Earth and Vulcan first established in Broken Bow, Part 1 (2001).
Jeffrey Combs, Vaughn Armstrong and Gregory Itzin are all Star Trek: Deep Space Nine (1993) veterans, as they all played at least two characters on that series. Combs and Armstrong both appeared in The Dogs of War (1999). Jeffrey Combs played Weyoun and Brunt and Vaughn Armstrong played Danar and Seskal.