Maulana Sher Mohammed Sindhi (later a khalifa) was corresponding with Hakim al Umma Maulana Ashraf Ali Thanvi (Allah have mercy on them). He had written almost 30 letters.
On a visit of stay at khanqah Hakim al Umma reviewed them all. He disapproved of the manner it was done. He instructed him to start over the islahi correspondence again.
Karwan e Mujaddid Thanvi, volume, page
This shows that islahi correspondence has to be done in a proper systematic manner.
This is the reason for encouraging the seekers to read the book ‘Tarbiyet us Salik’.
Writing in a haphazard way with pointless details and random thoughts is a total waste of time. Both for the seeker and the mentor.
If one does not know how to do this islahi correspondence then he/she should ask.