What was the Lewis Carroll reference and mockery to the Phoenix members?

There is a famous poem by Lewis Caroll called "Jabberwocky", which the e-mail adress Jabberwock12.listservharvard@edu seems to be referencing.

EDIT: As to the updated question, Mark is mocking them because to him those guys seem to pretend being sophisticated and literary by chosing this poem as e-mail adress. But it is actually a very famous poem, which is why Mark calls it "the world's most obvious Lewis Carroll reference". Add to this Mark's general cynicism/arrogance and dislike of the Phoenix Club members. So to him this reference isn't as elaborate as it may be supposed to seem and they are just boasting to seem like literary experts, while they aren't.

Eduardo Saverin: Jabberwock12.listservharvard@edu.

Jabberwocky:

"Jabberwocky" is a nonsense poem written by Lewis Carroll in his 1871 novel Through the Looking-Glass, and What Alice Found There, a sequel to Alice's Adventures in Wonderland. The book tells of Alice's adventures within the back-to-front world of a looking glass.

"Jabberwocky" is considered one of the greatest nonsense poems written in English. Its playful, whimsical language has given us nonsense words and neologisms such as "galumphing" and "chortle".