The data buffer created for the "MSExchangeIS" service in the "C:\Program Files\Exchsrvr\bin\mdbperf.dll" library is not aligned on an 8-byte boundary. This may cause problems for applications that are trying to read the performance data buffer. Contact the manufacturer of this library or service to have this problem corrected or to get a newer version of this library.
The Microsoft article "XCON: Message Transfer Agent Generates Event 1016 When Logging Performance Monitor Counter in Windows 2000 Server" (http://support.microsoft.com/support/kb/articles/q263/1/12.asp) describes this problem.
Event ID 1016 is an advisory telling you that the Win2K performance monitoring subsystem is receiving data that's not aligned on 8-byte boundaries. Windows NT didn't care, but Win2K does because 8-byte-aligned access is more efficient on some types of CPUs. The article mentions that Microsoft fixed this problem for the MTA in Exchange Server 5.5 SP4, but the fix evidently didn't make it to some other Exchange components.
You can safely ignore these messages.