You may wonder what will happen if there are multiple routing rules with the same priority.

In this case, there is no specified determination of what will occur.  Please find the following excerpt from the Routing manual:

2.5 Rule Evaluation

A rule consists of:

• A set of conditions, and
• A set of actions or counters

For a rule to match a message, the message must meet all conditions in the rule. The message may also need to meet certain parameters that are related to the rule's action.

Logically, all of a rule's conditions are combined by an AND operation. You can achieve OR logic by defining multiple rules. Also, certain types of conditions have intrinsic OR capabilities.

Evaluating Routing Rules

Every routing rules has a priority. When the RTR processes a set of routing rules, it starts with the rule that has the highest priority. If that rule does not match the message, the RTR continues to evaluate the rule with the next lowest priority. If multiple rules are defined with the same priority, the evaluation order is unspecified.

The evaluation process stops at the first rule that matches the message, and the RTR applies that rule's action to the message. If no routing rule matches a message, the RTR applies the default behavior of the rule set to the message.