WoWDB

To get this mount:

1. Download the Hearthstone game.
2. Win three games in “Play” or “Arena” mode to get the "Mount Up!" Hearthstone quest reward.
3. Log in to WoW and get the  Hearthsteed from your mailbox.

Learning the mount will also award the  Hearthstoned achievement.

Letter from Mei Francis:

<name>,

This fine magical construct arrived only yesterday, and you were the first adventurer I thought of.

Enjoy!

Mei Francis
Exotic Mounts
Dalaran

It is worth noting that the mount gets mailed to the first character you log in on after earning the achievement, so make sure you don't log in on your level 1 bank alt, unless you want to have to level him to 20 to train the mount.

I'm sure one could resolve it with a ticket, but you can avoid all that entirely by just making sure you pick up the mount on a character that can learn it.

I actually had the mount mailed to every character that I logged in to. However, I believe the key difference is that I did not loot it from mailbox. Once I actually grabbed it from my mail, it didn't seem to keep mailing (as characters that I logged in to after that didn't have it in their mail).

The red version is not available to players at this time. There hasn't been official word on the exact reason(s) for its unavailability. It is speculated that Blizzard originally intended the mount to be faction thematic, then later determined that the mount should be thematic to Hearthstone - which is the color blue.

It is always possible that Blizzard will make use of the red version in the future.