So i'm just starting to GM SRM03-05 in a pbp game and I recently ran into a problem. Other than planting the evidence and making NYPD Inc look bad (both secondary objectives), why would Mrs J hire runners to deliver a message to an inmate when it would be simpler to just bribe someone who comes in contact with the inmate to deliver the message (ie a guard, the lawyer, a nurse in the facility, anyone who visits the inmate during visitation, etc)?

She wants a cutout between herself and the messenger. You hire shadowrunners to be that cutout.

The shadowrunners are the messenger. So she's still dealing with the messenger, just an overpaid group of messengers (ie runner team).

It's also not just delivering a message. If it came down to just a messenger, yes, the runners could just as easily subcontract out that part of the mission. But (trying to keep the spoilers to a minimum) there's other stuff the runners have to do to make sure the recipient follows the message.

You do have a point, though--this mission can be as hard (or as easy) as the runners decide to make it. It seemed to be relatively straightforward for the team I played with, certainly easier than the prequel mission.

Some of it is to get the PC's involved, some of it because the prision obviously has safeguards in place to make that difficult. Subverting those safeguards is a job for runners. In this case it may be better to presume that there are reasons it could not be done simply rather then questioning why it could not be done simply.