Abbreviations and so-called "text-speak" have become a huge part of our society. Why say "you" when you can simply type "u?" It's perfectly fine to use this lingo when e-mailing friends or family, but it should have no part in professional e-mails. That seems like a no-brainer but you'd be surprised how many job seekers don't follow this rule. Just check out this example from a job seeker posted by About.com:
i would like to put an ap in are u able to fax me a ap i didnt do up a resume yet i am working on it u think we could work somthing out thank you!Yikes. Besides the obvious punctuation and grammar errors, note that this person is using an abbreviation for the word "application." Just because something is obvious to you doesn't mean it will be obvious to your reader. It shouldn't take more than a second for the reader to understand what you are trying to say.
When you are e-mailing about something as important as job, there simply is no excuse for there to be errors of any kind. Have someone else read your e-mail before you send it out. The best way to make sure your writing is error free is to have an outside party look it over. If it passes the smell test with that person, you should be good to go.