Today, it is considered that a person who holds a management degree is far superior compared to a person who is just a graduate. Such is the demand for management graduates that a lot of engineers are quitting their high paying jobs and opting for management courses and a career in management. Such a surge has occurred largely due to colleges like the IIMs, XLRI, NITIE, etc. So people are starting to join the rate race of getting into these institutions right since the beginning of their graduate career. So it has become a simple case of too many applicants and too less seats. At the end of the day, many people are left out and some of these include people who are deeply motivated to not sit out for a year and wait for next years admissions. These people choose the correspondence course option, along with the people who are working part time.
MBA by correspondence differs from part time MBA in many ways. One being that in part time MBA, the lectures are held on weekends whereas in correspondence courses, lectures are not held at all. The other aspect in which they differ is that part time MBA takes a longer time to complete as compared to MBA by correspondence. Almost all the leading institutions offer MBA by correspondence and this is a course on par with the regular courses, as the exams are held at the same time as those of the regular courses.
Thus, opting for a MBA by correspondence can be a beneficial decision, as you don't have to be actually present in the colleges. But this has its own deficits, the basic one being lack of exposure to working environments. The person pursuing a MBA by correspondence is not used to working in teams and this may hamper his chances of securing a good job.