Almighty Allah has appointed angels to convey Durood to the Holy Prophet (Sallallahu alaihi wa sallam)
For some reason, the Holy Prophet (Sallallahu alaihi wa sallam) did not reveal His knowledge at that moment, which is expressed in other Hadith. Otherwise it cannot be that Almighty Allah grants one angel such a great amount of knowledge (of hearing the Durood of everyone) and doesn’t distinguish His Beloved Prophet with greater knowledge.
Thus a single angel hears the Durood of the whole earth and conveys it to the Holy Prophet (Sallallahu alaihi wa sallam) at that very moment. This is apart from the Durood which goes to the ‘Arsh and then comes to the Holy Prophet (Sallallahu alaihi wa sallam). Apart from this, other angels are also appointed who convey Durood to the Holy Prophet (Sallallahu alaihi wa sallam).
This we learn from the following Hadith:
The Holy Prophet (Sallallahu alaihi wa sallam) said: When a person sends Durood to Me, an angel brings it to Me. I reply: Convey 10 Durood to that person on My behalf and if even one of them is conveyed, that person will enter paradise along with Me and I will intercede for that person. (Waseelatul ‘Udhma)
Similarly, there are many angels who convey the greetings (Salaam) to the Prophet. They are forever in search of it. Wherever someone sends greetings to the Holy Prophet (Sallallahu alaihi wa sallam), they convey it to Him.
There is a Hadith in Masaalik Ul Hunafa:
Translation: The Holy Prophet (Sallallahu alaihi wa sallam) said: Allah Most High has appointed many angels who keep traveling and convey the greetings of My Ummah to Me.
[Excerpted from Anwaare Ahmedi]