Mikhail is a Human quest-giver (level 30) located in Deepwater Tavern in Menethil Harbor in the Alliance-aligned zone of the Wetlands.
Although he (apparently) is a Bartender by his title, he doesn't actually sell any drinks. He is also a former rogue and in touch with the SI:7.
See List of Wetlands NPCs.
Patch 1.2.0 (18-Dec-2004): Fixed the problem that was causing Mikhail in Menethil Harbor to become inactive after someone failed the quest of The Missing Diplomat.