What is the extent of a qualified plan's responsibility to pursue survivors and beneficiaries?

[MMMBENE2000]

In some of our DB & DC multi-employer, qualified plans, we have sent applications out to surviving spouses and beneficiaries (for J&S survivor benefits on DB or distribution options on DCs, for example) and not received responses (nor returned mail). By the way, this question is applicable to participants and beneficiaries that are all under 70 1/2.

To what extent must we pursue these situations? Send the app and just wait until the RMD rules kick in? Send a few regular reminders and then send a formal denial (based upon not submitting an app)? If this (under 70 1/2) pursuit is in the regs, can anyone give me the reference?

Thanks!

[GMK]

A couple of links to get started:

http://www.irs.gov/Retirement-Plans/Missing-Participants-or-Beneficiaries

http://www.401khelpcenter.com/401k/missing-plan-participant.html#.VdzRUOmFNaQ