Essex Head Coach Paul Grayson said he was delighted Mahmood had joined the club.
"I like cricketers who feel they have point to prove to people and he has lots of ability, he's experienced and he's a fit guy who can bowl with good pace as well so we feel Saj will be a real addition to the squad."
More top news
A military medic from Cambridge who survived Ebola says that she had no qualms about trying the experimental drug MIL 77.
A police officer from Northampton is being held on suspicion of murdering his wife.
It will be a windy weekend with occasional outbreaks of rain.