Acts of violence
Films of hostages and beheadings were also discovered.
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 websites have become an effective means of communicating such ideas."
However, he also said that none of the men, who were alleged to have close links with al-Qaeda in Iraq, had come close to carrying out acts of violence themselves.
"Incited to murder"
In a separate court case in London, a web designer was convicted of inciting murder during a protest over cartoons of the Prophet Muhammad that were published in a Danish newspaper.
Mizanur Rahman, 24, had called for British soldiers in Iraq to be "brought back in body bags" and for "9/11-style attacks" in Europe.
He was arrested after making the remarks via a loudspeaker at a demonstration outside the Danish embassy in London early last year.
Peter Wright, the prosecutor, said Rahman "incited or encouraged others to murder in the name of religion".
Footage of the protest showed Rahman saying: "We want to see them coming home in body bags. We want to see their blood running in the streets of Baghdad.
"We want to see the mujahideen shoot down their planes the way we shoot down birds. We want to see their tanks burn in the way we burn their flags."
He also had placards calling for the beheading of people who insulted Islam.