With NAVTEX Distress alerts, navigation and weather warnings cannot be rejected.
The same providers of the NAVTEX also provide information to the SafetyNET. Navigational warnings are provided daily to NAVAREA IV at 1000 and 2200 hours UTC. NAVAREA XII is broadcast over POR satellite at 1030 and 2230 UTC.
The COMSAT CES at Santa Paula, California provides MSI service to the Pacific Ocean Region and MSI service to Atlantic Ocean Region EAST and WEST.
By-the-way there are special receivers that may interfaced to INMARSAT-A or B to allow for EGC in addition to the normal communications, to allow for receiving the SafetyNET.
A third method of receiving Maritime Safety Information is High Frequency Radio.
If we look at the FCC rules in 47 CFR 80.1123 (b) we find that while at sea, all ships must maintain radio watches for broadcasts of maritime safety information on the appropriate frequency or frequencies on which such information is broadcast for the area in which the ship is navigating.
This would mean that if your ship is in the area not served by INMARSAT then you must set up watches on those frequencies that would be in use in that area. Of course this does not mean that if, in any sea area, you cannot use the HF frequencies to receive MSI in lieu of any other method. On HF radio there are special frequencies for reception of MSI via NBDP. The IMO GMDSS Master Plan Publication identifies HF Coastal Radio Stations that broadcast MSI via NBDP. It seems reasonable that HF NBDP is required in sea area A4 outside of NAVTEX service areas.
