The letter looks like any other official document. It's on headed paper. There's a stamp. There's even a logo in the corner. So far, so bureaucratic.
The content, however, is far from bureaucratic. It's a letter listing demands from the Islamic State group and a response to previous request asking leaders of Mosul's Christian community for a meeting.
The demands are blunt. Christians either convert to Islam or pay a tax that allows them to continue to practice their faith. The letter goes on to say that the decision was taken after Christian leaders in the city failed to attend the requested meeting.
The letter states they should leave the city without taking any belongings with them, and that a death penalty is the "last resort".
Other pictures sent to Al Jazeera show Christian houses marked and declared properties of the Islamic State.
From the mosques, Islamic State imams reissued the demands after Friday prayer.
Under the Ottoman Caliphate a tax, the jizya, was levied on non-Muslims. It was designed to show that non-Muslims accepted Muslim rule, and that in return they were free to practise their religion and were afforded protection from aggression, both internal or external. The Muslims also paid a tax, zakat, to the empire.
The Islamic State has levied this tax before, in territories they control in Syria, and have issued similar decrees.
Church leaders in Iraq or indeed in Mosul haven't responded to the threats officially and sources inside Mosul believe that most of the community fled after churches and shops were smashed and they were denied food by the group.
Between June 10 and June 30, according to the UN, at least three churches in the city had been taken over by the Islamic state, previously called ISIL, and that the group planted thier flag on top of the buildings. The UN also says that houses of Christians who had fled had been looted.
But the city itself is far from a united capital of the "caliphate". The eastern side is dominated not by the Islamic State but the one of the main Iraqi Sunni rebel groups, the Naqshbandi.
They've replaced Islamic State flags with their own and are in control. But to what degree is being questioned. According to our sources an agreement has been made between the Islamic State and the Naqshbandi giving the Islamic State overall control of the city, but the situation is complicated.
Even those left behind are confused as to who is in charge. "We just avoid anyone who has a gun. I stay at home and I don't want to be noticed. This is is now my life, hiding in the city I was born in, that I've lived all my life," says Faisal, not his real name, who I've been speaking to in Mosul since the city fell on June 10.
The Iraqi military say they carry out regular air attacks against rebel and Islamic State targets in the city but so far no major ground offensive has begun. The reason that Mosul remains in the hands of the rebels groups is that Iraq doesn't have the troops to retake the city.
One Middle Eastern diplomatic source told me that the sectarian nature of Iraq's army was a problem.
"The army is mainly Shia, and Iraq is also using Shia militias. Send troops who are mainly Shia to Mosul to fight agianst the Sunni rebels will turn this insurgency into an all-out civil war with the Sunnis. It's better that the
Sunni tribes and the Kurdish Peshmerga fight, to avoid sectarian escalation."
So far the Sunni tribes, who have said they will fight the rebels and the Islamic State, have maintained they will not take up arms until Nouri Al Maliki, quits as prime minister. Maliki shows no desire to do so and his party is insisting he is the only one who can lead Iraq out of this crisis.
The Kurdish Peshmerga, the Kurdish regional force who control the borders of Mosul, are also waiting for a political decision from Kurdish politicians before they enter the city. Both those forces will be crucial if Iraq wants to defeat the Islamic State and the Sunni Rebels.
For now Mosul remains the capital of the "Islamic State" and an Iraq city under siege. It's a situation few can see changing in the near future.
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