Bethesda, via a Tweet, on its official page has notified its users that the Doom Multiplayer and SnapMap servers are down right now.
The detailed notification on the official forum reads:
We will be performing server maintenance at 12pm ET today. The maintenance is scheduled to last for two hours and will affect access to the Multiplayer and SnapMap servers. For clarity, this is strictly server maintenance and is not the Free Update 3 patch, which will be going live next week. We’ll provide an update when the servers are back online.
Thanks for your patience!