What limits the obligation of congregational prayer for one who is outside the town?

The questioner : I say, Shaykh, for a man who is outside the town, the obligation is limited to a certain extent.

The Shaykh : What appears to me is that this is limited by hearing the adhan. If he is outside the town, it is by hearing the adhan. The intended adhan is the customary one, not the sound of loudspeakers, because the sound of loudspeakers reaches a far distance.

The questioner : But the mail, Shaykh, some scholars say, Shaykh, that it is obligatory when it arrives at the specified time after the delay?

The Shaykh : No, no, that is not correct. It is due to hardship.