Moroccan-born Tsouli, 23, was jailed for 10 years; UAE-born Al-Daour, 21, received a six-and-a-half year sentence; and 24-year-old Mughal, who was born in Britain, was given seven-and-a-half years.
Sentencing them, Judge Charles Openshaw said the men had engaged in "cyber jihad", encouraging others to kill "kuffars" or non-believers.
He said: "It would seem that internet web sites have become an effective means of communicating such ideas."
However, he also said that none of the men had come close to carrying out acts of violence themselves.
The trial was told the computer experts spent at least 12 months trying to encourage people to follow the ideology of Osama bin Laden, al-Qaeda chief, using email and web sites.
Films of hostages and beheadings were found among their possessions, including footage of British contractor Ken Bigley, who was killed in Iraq in 2004; and US journalist Daniel Pearl, killed in Pakistan in 2002.
Compact discs containing instructions for making explosives and poisons were also found, with other documents giving advice on how to use a rocket-propelled grenade and how to make booby traps and a suicide vest.