You can go to Hellfire at 58.
You can get to Outland by using the Shattrath Portal in Stormwind Mage Tower or the retail Orgrimmar Portal Room. You can also talk to the mage near the portal [H] or at the tower entrance [A] to get to Hellfire Peninsula. In Classic, you must use the Dark Portal in Blasted Lands instead.
A player is asking on the forums how to report someone under level 58 in the Outlands as there is a level restriction for the Dark Portal, which means you must be level 58 before you can go through it can.
Now the requirement to enter Ramparts is level 57 (the same level you can queue at) but the quests for the Outlands are still 58. no… just no… Outlands isn’t worth going to at least 58. But with the new low-level quest, you can easily stay until 62.
Hop on your mount or form of travel and make your way south to the Blasted-lands. At the very bottom there is an area called “The Dark Portal” where you will find the actual Dark Portal itself, the entrance to Outland.
Entering Outlands is possible at any level if you have access to a Shatten Mage Portal. for quests it is lvl 58.
Take the Dark Portal to Outland and bring the portal back to Orgrimmar. It should be on your left once you reach the Staircase of Destiny (with your back to the Dark Portal).