Captain Kirk,
I want to firstly express my gratitude for your generosity and hospitality in allowing me to serve aboard your ship. It has been an honor and a privilege, not to mention highly enjoyable. However, I regret that like all good things, this arrangement must come to an end.
Given the unknown nature of my current circumstances (specifically, how I have time-traveled and universe-jumped), I cannot be sure of how time passes in relation to my native reality, and therefore I believe it most prudent for me to attempt to make my way home as soon as possible. Towards that end, I will be departing the Enterprise before she leaves orbit.
I bid you farewell and wish you and your crew the best of luck on your five-year mission.
Sincerely,
Dr. Julian Bashir
Dr. McCoy,
I'll be leaving the ship soon, but I want to thank you for letting me work alongside you in your sickbay. It was a wonderful experience, not to mention an honor. Good luck on your five-year mission, and don't worry, medical tricorders will get more accurate in the future.
Sincerely,
Julian Bashir