A few of mine (fortunately I read and re-read emails before hitting send):

Hope to hear from you shorty

Kind Retards

....placed Mike in your tea

Not a typo, but I also thought this was funny, this chap recently won some kind of award here in the UK for best recruiter gaffes:

“My ex-girlfriend was pregnant and at home feeling sorry for herself.  We had just bought some new furniture including a two-seater armchair with a cringe-worthy name.  I was in the process of emailing a client with some important info for a contract I was on the verge of winning when she emailed me to say she was having a rubbish day and wanted me home.  I, of course, got the emails mixed up and sent one to my client saying: ‘Not long now babe and I’ll be home where we can cosy up in the snuggle chair.’

“Shortly after I received a jokey email from client saying: ‘Thanks Iain but don’t think my wife would be too happy.’

“I couldn’t hide my embarrassment and was the talk of the office for weeks.  However, I did manage to then supply seven candidates to said client on good fees, so every cloud eh!”