Mercury is the messenger God, and the planet of communications ruling both Virgo and Gemini. I know it’s hard to imagine this because astronomically speaking, Mercury makes one rotation around the sun in about 88 days, so it appears to be free of the sun, but astrologically speaking, Mercury is very limited.
Mercury never strays more than 28 degrees away from the sun.
For example, Mercury can only be in Sagittarius if the sun has reached at least the 3rd or 4th degree of Scorpio, is in Sagittarius, or hasn’t passed the 27th degree of Capricorn. Basically, Mercury can only be in Sagittarius during the sun’s transits of Scorpio, Sagittarius, and Capricorn, or at some point between November and the middle of January.
This is one of those things about astrology people don’t give much thought to, but this knowledge does have its place of importance somewhere.