Final answer:
Grammatical and spelling errors in a letter are not likely to convey professionalism or credibility, which can lead to a negative impression on the reader.
Step-by-step explanation:
When grammatical and spelling errors are present in a letter, it is NOT likely that the letter will make the best impression on the reader.
Errors can undermine the credibility of the writer and suggest a lack of attention to detail, which may lead to the reader questioning the professionalism of the content.
It is fundamental to use correct spelling, proper grammar, and to proofread carefully to ensure that your message conveys respect and seriousness to the recipient.