Writing an email is equally important as writing a physical letter. The difference is only that email if free of cost while physical letters charge us some amount to send them. But this free factor has literally spoiled the etiquette of people with respect to writing an email. They consider it as a free tool of spamming and using instant messaging language. There exists zero professionalism in emails these days.
So let's discuss some points which shall be kept in mind while writing and sending emails.
Cross check the email address: Check the email addresses at least two times before you hit the Send button, because a wrong ID can lead to several consequences like non-delivery or wrong delivery of the document.
Include appropriate subject: Always include an appropriate subject heading to your mail, as it will increase its' relevance. Avoid subjects like Hi..., Query..., etc. These subjects make your email less relevant and chances of its deletion or non-reading increases.
Don't use all capital letters: Never use all capital letters either in subject line or mail body, as this seems like shouting or giving order to the recipient. It also leaves a bad impression about your personality.
Correct Salutation: Use right salutation for the person to who you are addressing the letter. Take care of Mr. or Ms. and never get confused with them. Well! It could lead to disasters also.
Precise message: Keep in mind to make your message precise and to the point. It doesn't mean at all that it shall be very brief, in fact it shall be explanatory with extra stories stuffed into it.
Attachments: Make it sure that you don't send very heavy attachments along with emails, because some servers don't allow them. Then your all pain would go in vain. If your file is heavy, compress it and then send it. Always mention about the attachment in the message body, otherwise it might get ignored.
Include original message: Try to include previous or original message below the mail in case you are responding to a mail. This will increase the relevance of the conversation.
Spell check: Cross check the spellings before sending the mail. Otherwise if you feel it tedious to read the whole mail again, turn on the Spell Check option of your email server.
Warm Ending: End your email with warm greetings like Warm regards, Best Wishes, etc. This would leave a good impression of your persona on the reader.
Follow up: Last but no the least, pick up the phone and make a follow up call for confirmation of receipt of mail. This will reflect your positivity and zealous nature.
If you will keep all these points in mind before writing an email, for sure you will end up with a good one. Try these tips and you will be able to create a really nice and professional looking letter.