I received a hand-addressed envelope in the mail containing a hand-written thank you card:
[Zorak],
Thank you for your continued loyalty to Delta! We are honored that you've chosen us to be your preferred airline of choice for your travel needs.
We look forward to seeing you again soon at SFO!
All the Best!
SFO Sky Club
The envelope flap was sealed with a blue sticker with the red widget and "The SFO team thanks you for your business. We always strive for 5!"
I'm not sure how they know DL is my preferred airline, maybe I fly even more on other airlines

(I don't though

)
Anyone else get this? I'm kinda surprised they went to the trouble for a low-MQD DM
Also kinda surprised to receive a note from the club itself -- wouldn't have thought a lounge could have agency