At some point during BFA, Blizzard removed the Blasted Lands portal from Orgrimmar. Now there is supposed to be a dialogue option to teleport to the Blasted Lands when talking to the Thrallmar Mage in the Orgrimmar portal room. However, my main character does not see this dialogue option.
What is the requirement to unlock this?
Based on the Wowhead discussion of the NPC there isn't a definitive answer, but it seems that you have to be on one of the Outland breadcrumb quests, for example Warchief's Command: Outland.
As of patch 9.0.2, the Thrallmar Mage now has the "I must report to the Dark Portal" dialogue option for all of my characters.
However, the behavior of the teleport changes depending whether or not I'm on the Burning Crusade: To Outland! quest. When my character is on this quest and I take the teleport, it puts me in the Blasted Lands, outside of the Dark Portal. If I'm not on the quest and I take the teleport, it puts me in Hellfire Peninsula, just inside the Dark Portal.
Unfortunately it also seems you can no longer walk into the Dark Portal to get back into the Blasted Lands, so if you aren't on the Outland intro quest, the Thrallmar Mage will not help you get to the Blasted Lands.
