I am still in my 70s and contribute to employer's IRA plan. I believe I don't need to take an RMD on this. But what about IRA holdings I have from other accounts?

Are you contributing to an employers's IRA plan or a 401K plan? An exception is made for RMDs on your 401(k) if you are still working. If you are working after age 70½ and you are not a 5% or more owner of the business, then you can delay distributions from your 401(k) at the company you work at until April 1 of the year after you retire. However, f you have other IRA accounts the RMDs are still required on those.