In order to delete emails from the Axigen queue matching a pattern you will have to use the CLI interface. 

Login to the CLI interface please use the following command:

 telnet "Axigen IP address" 7000

<login> user admin

<password> "admin password"

Next issue the following command in order to enter the Queue context:

<#> ENTER QUEUE

You can type "help" any time to view all the available commands for the current CLI context.

<queue#> HELP

In order to list the messages which have a specific recipient type:

<queue#> LIST FILTER recipient="string to match in the recipient's address"

To delete these messages found with the previous command type:

<queue#> DELETE lastFilter

You can quit CLI at anytime using QUIT.