The assertion is informing you that the system it is running on has NO
virtual memory meaning that there can be no "Page swapping", this is
unusual but not an actual error in itself although it is very likely to lead to a system crash or system freeze if ANY virtual swap memory is needed. This is a problem for just about everything that runs on this system, it is not an email related error at all, however the mail subsystem just happens to be one of the few things that reports it.
Solution: Set the amount of vrtual memory on this system to something other than zero,lol.