Been using your service for quite a while and hadn't run into any issues, all was working. In the last month or two I've noticed that I cannot receive SMS messages to my IM client from people not on my contact list. Example, receiving 2 step auth numbers from google delivered via SMS. These will go to my email with a message from gvmax stating I was offline. However any sms from someone on my contact list comes through fine directly to my im client. This is on multiple IM clients, but I mainly use pidgin. I would just add them all as contacts but I have no idea how many numbers google delivers these messages from and there must be some issue here if I receive messages from contacts no problem. Again, this all used to work fine and I have not changed anything with my filters etc.
Edit - I'm not sure why, but I (appear to have) fixed this problem by using the same application specific password for signing into gtalk as used for gvmax settings for gtalk.