Dear Miss Snark:
I'm an editor of a small newspaper in the midwest. I don't read or respond to email coming from hotmail.com. I don't feel that way about gmail or yahoo addressess, however.
Do literary agents discriminate against email domains in a similar way?
However, I do look at email NAMES. If your name is "2hot4words" at whatever dot com, I'm probably not likely to open your email.
Same if you put a subject heading along the lines of: this needs your attention.