Malowned

Malowned is rewarded from defeating [npc=11143] during Pet Battle Challenge: Stratholme. Defeating [npc=11143] gives the pet [npc=155865] .
To summon Postmaster Malown, you must find the 'Discarded Letter' that can be found in multiple locations, on both difficulties.
After obtaining the letter, bring it to the letter box during stage 7 at 57.65. 13.71 to summon Postmaster Malown.

Warning! If not defeated for approximately 20 minutes, Postmaster Malown will leave, and even if you reset the dungeon, he doesn't come back!

/way 68.92. 54.01 (Stage 1)
/way 59.71. 40.56 (Stage 1)
/way 56.92. 50.81 (Stage 1)
/way 57.79. 36.89 (Stage 6)
/way 40.24. 10.42 (Stage 10, accessible on stage 9 but might as well complete the stage)
/way 57.65. 13.72 Bring letter here!

I found mine Discarded Letter at 56.87 50.88 on Stage 3 just next to the Crypt Fiend

You do not need to find the letter and defeat him at stage 7. I Got very confused from the comments saying he spawns at stage 7. Just complete the dungeon and then go look for the letter at every box and crate in the instance. Once you find it you just go to the mailbox at /way 57.65. 13.72 and then defeat him within 20 minutes.

This fight isn't terribly difficult. He has an Undead > Magic > Undead. You'll want something faster with a dodge to avoid Curse of Doom when it's up, but beyond that you should be okay to have:

*Critter/Aquatic (with critter damage)
*Non-Dragonkin with Dragonkin attacks, preferably a Beast
*Critter/Aquatic (with critter damage).

For example:
Tolai Haire: 2/2/2, Speed > 311
Dreadmaw: 2/1/2
Any level 25 critter

Turn 1 Dodge
Turn 2-4 Stampede
Turn 5+6 Flurry (2 hits)
Undead Dodge
Plagued Mailemental comes in
Turn 1+ Stampede until Mountain Cottontail dies
Bring in your Dreadmaw
Turn 1+ Flame Breath until Plagued Mailemental dies
Soul Collector comes in
Turn 1 Glowing Toxin
Turn 2+3 Burrow
Turn 4+5 Flame Breath (2 hits)
Turn 6 Glowing Toxin
Turn 7 Flame Breath
Turn 8+9 Burrow
Turn 10+ Flame Breath until Soul Collector dies
If needed:
Bring in your Critter pet
Any standard attack will finish the fight