[OMPI users] Are the Messages delivered in order in the MPI?

[Mateus Augusto]

I would like to know if the MPI is a FIFO (first in first out) channel, ie, if 
the A message is sent before of the B message, then, MPI garantees that A will 
be received before B in the recipient.
Does the MPI guarantee that A always will be received first?
Or may B be received first sometimes?
Assume that A and B are sent in different calls to send messages (for example 
MPI_Send).