Should the Mu’adhdhin Pray behind the Imam?
Question

Is it Sunnah for the Mu’adhdhin  to stand directly behind the Imam 100%?
I hope that you can advise me so that we can put an end to an argument in the mosque.
Praise be to Allah.Is it Sunnah for the Mu’adhdhin  to Pray Behind the Imam?
With regard to the Mu’adhdhin  standing behind the Imam, there is no specific Sunnah that is proven from the Prophet (blessings and peace of Allah be upon him).
Who should stand behind the Imam?
The only thing that is narrated concerning that is that it is recommended for those who are most wise and dignified to be closest to the Imam. The Prophet (blessings and peace of Allah be upon him) said: “Let those who are most wise and dignified be closest to me”. (Narrated by Muslim, 432)
The Best Position for the Mu’adhdhin  After the Iqamah
But there is nothing wrong with leaving a space behind the Imam for the Mu’adhdhin  to stand when he has finished reciting the Iqamah or call immediately preceding the prayer, so that he can find a suitable place in which to pray without having to cut through the rows. And there is nothing wrong with this place being slightly to one side of the Imam, to the right or left.
For more details, please see the following answers:
Is it permissible for the Mu’adhdhin  to be the Imam?
Responding to the Mu’adhdhin  is better than reading Quran
Ruling on the Mu’adhdhin  taking a few steps whilst reciting the Adhan
Is it permissible for the Mu’adhdhin  to give the Adhan whilst seated?
And Allah knows best.