defaultexpiry setting for providers in webadmin
Some VoIP providers do not allow defaultexpiry below 3600 seconds. Therefore its important to adjust the defaultexpiry to the providers required setting otherwise you'll get:
[24 21:15:19](May) WARNING[3485] chan_sip.c: Got 423 Interval too brief for service XXXXXXXXXX@tel.t-online.de, minimum is 480 seconds
This setting needs to be set for each peer, not for "general" config. sip_devices is the table to look at: set session-timers to refuse and session-timers to NULL