When learning a second language, it is important to be open to different sounds that are not present in your native language. There are some fairly obvious ones such as tones in Chinese and clicks in Zulu and Xhosa but most languages will contain some sounds that you are not familiar with. I remember spending quite some time in French class at school trying to replicate the nasal n, the r and the eu sounds.
When writing an email or letter, whether private or professional, it is a good idea to do a review before you send it off. This is your chance to make sure the tone is right; not too aggressive for example. It is also an opportunity to check for some of these easy to make errors.
Whatever your document is, website content, advertising material, a proposal, or report, it is always worth having your document reviewed by a second person. It is hard to review your own work as your eyes skip over the errors because of over-familiarity and you may be blind to your style issues such as overusing a particular word. This becomes even more important if English is not your first language.