Dear Saunak, you have not mentioned the context under which you have raised this query. Is your query from the employer's point of view, or is it that as an employee you have come across an actus reus of someone and you wanted to bring it to the notice of the management but at the same time you want to protect your identity?
Other than the suggestion box or survey, the only method left is writing to the MD anonymously and sending the details by courier. However, many times, rather than reaching the MD, letters of this kind find their way to the trash can.
The word "anonymous" in your post brings to the fore the crux of the matter. Whether you have written the post from the viewpoint of the employer or employee, this very word suggests that employees are wary of giving suggestions or feedback to their seniors. Therefore, what is important is to create a culture where juniors give feedback without fear of reprisal. If some employee is engaged in insalubrious activity, and if other employees look the other way, how much loss the company could be incurring cannot be estimated.
You wanted to engage the employees by creating a channel for upward communication. However, the essence of employee engagement lies in open and transparent communication. When employees want to hide under the guise of anonymity, it symbolizes their lack of trust. It also symbolizes they have a fear of conflict either with their peers or superiors. Otherwise, these employees could be well-wishers of the company but do not want to be open whistleblowers. Why do they wish to blow their whistle privately is a point to ponder!
Thanks,
Dinesh Divekar