I know that the RMDs are suspended for 2009, however, are we still required to mail something to the customer letting them know they may but are not required to take a distribution?

IRS Notice 2009-9 states that "the RMD information required under Notice 2002-27, 2002-18 I.R.B.814, need not be sent to IRA owners for 2009."

http://www.irs.gov/pub/irs-drop/n-09-09.pdf

Just to clarify, you were required to either report the client's RMD for 2009 as "$0" or if you could not update your 5498 in time you were required to send a notice to your clients informing them that they were not required to take an RMD. You do not have to inform them that they "may" take a distribution, as this would just be an ordinary normal distribution, not an RMD.