Source:https://www.lifewire.com/fundamental-email-etiquette-1171187
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Do You Make These Mistakes with Email Etiquette?
The rules of email etiquette are not “rules” in the sense that I will come after you if you don’t follow them. They are guidelines that help avoid mistakes (like offending someone when you don’t mean to) and misunderstandings (like being offended when you’re not meant to).
Take Another Look Before You Send a Message
How to avoid embarrassing emails and not send anything you do not want sent.
Do Not Default to “Reply All”
“Reply” is good. “Reply to All” is better. Right?
Keep Emails Short
Properly Format Your Email Replies, and Be Lazy
Write Perfect Subject Lines
Clean Up Emails Before Forwarding Them
When in Doubt, Send Plain Text Email, Not Rich HTML
Don’t Forward Hoaxes
Use Antivirus Software, Keep Up to Date, Scan for Free
Make sure you’re not spreading worms and viruses via email or act as a vehicle for spreading spam. All this can be caused by malicious emails. Fortunately, there’s protection.
Explain Why You Think What You Forward Will Interest the Recipient
Do Let People Know Their Mail Has Been Received
Did the spam filter eat my message? Spare others this nagging question and let them know you got their email.
Talk About One Subject per Email Message Only
Punctuation Matters; in Emails Too
Use Acronyms Sparingly
Resize Pictures to Handy Proportions for Emails
Writing in All Caps is Like Shouting
Catch Typos by Printing Your Emails
You can often find typos or misplaced commas neither your spelling checker nor you yourself catch when proofreading on the screen.
Avoid Embarrassing Emails
Avoid embarrassing emails by sending them to yourself only (by default).