Time is money, and time is a resource that cannot be squandered. Often editors work on more than one project at a time and this further bites into both their available time and resources as well as their sanity. When querying your editor always tell them which publication you wish to write for. Never send your query from an e-mail address that will bounce. Always spellcheck your work.
Nothing is more off-putting than a poorly edited article.
Now grammar is not everyone's strong point and neither is spelling, editors understand this. But if you can't go to the effort to spellcheck your work, then you are not bothering to put in any effort at all. Always study the publication you are submitting to. Not only will this prevent you from sending an inappropriate query, it will also help you to tailor your article to the publication's format. Always submit a bio with your article.