Is there a temporal sequence of message delivery?

Between a given sender and receiver, message sequence is preserved; that is, if process A first sends message M1 and then later sends message M2 and both messages are received by process B, process B will receive message M1 before it receives message M2. However, there are two special exceptions:

1. If process B receives message M1 and then rejects it, message M1 is redispatched to process C. In the meantime, (while process B is deciding whether to reply or reject message M1), the ToolTalk service continues its message delivery. These subsequent messages can appear to "pass" the first request.

2. If process B's messages are queued, it will receive its queued messages when it declares a ptype that contains the pattern which caused the queuing. However, process B may not actually receive its queued messages (in this case, message M1) until it has already received subsequent messages from process A.