After finishing the questline you will obtain the Heritage of the Sin'dorei. Speak with him and accept the starting quest: The Pride of the Sin'dorei. If you meet all the requirements then head over to the Orgrimmar Embassy and look for Ambassador Dawnsworn. Run it on Normal difficulty over and over, slay every single mob you can find, and they will give you reputation as long as you keep the tabard equipped. The best dungeon for farming reputation is The Mechanaar in Netherstorm. You can gain a lot of reputation by questing in Eversong Woods, but that might not be enough for Exalted. There are also no related achievements for unlocking it, therefore we have added the Heritage of the Sin'dorei to our Secrets Database. Note that the Heritage of the Sin'dorei transmog set is hidden and does not show up in the Appearances Tab until learned.
To unlock the Heritage of the Sin'dorei you will have to level up a Blood Elf character toreach Exalted with Silvermoon City and then complete a short questline starting with The Pride of the Sin'dorei. The Heritage of the Sin'dorei is the heritage armor set for Blood Elves.