[SR-Users] Handling timers from an Avaya PBX (throwing 404s)

Hi there, I turned up a few new sip trunk customers this past week, from which one of them was an Avaya system. The customer wasn¹t able to do a username/password auth, so I set them up as a permanent entry in the location table. I am running Kamailio 1.5.5. The issue is that I am throwing back a 404 to them when they do a timer event, as they are passing sip:Unknown@my.ip.addr. I don¹t have a user name Unknown, hence the 404. I noticed that with the timer events from other customer¹s PBXs, that they are passing sip:my.addr, from which I am giving back 200 OK. What is the best way to handle this? Just let it go or add a ³Unknown² user (I don¹t like the latter, really)? Calls to and from their system is fine, so right now it¹s just entries in my logs ­ but I hate spending CPU cycles on stuff that isn¹t going to benefit anyone. I sent an email back to the customer to see if maybe he can resolve it on his end, but I am doubtful on getting it resolved on his end. Thanks, -graham