Would you consider a resume sent as part of a job application to be business correspondence? So would I. Yet when my husband asked a young woman who responded to an ad for assistance why she did not capitalize (the word) "I," she replied that she would know to capitalize it on work documents. He did not find that a convincing enough answer to offer her an interview.
The ad we placed, which prompted the above response, specified that we were looking for someone who pays meticulous attention to detail and English grammar. While we met some highly qualified and impressive people, the bulk of the responses inspired the immediate use of the delete button. The "i" was so egregious that we couldn't refrain from asking about it, but it was by no means the only blatant error.