10 Tips for professional-looking emails

1. Start with a Meaningful Subject Line
   Your subject line can make or break your email. It may be the difference between your email being read or ignored completely.  Make your intentions clear but keep it short and to the point. Under no conditions should you ever use the subject line to write your entire email.  No one needs that clutter in their inbox. Many email clients, especially ones on mobile devices, will crop the length. Cutting off your message.
2. Address them properly
   Knowing your audience is important here. Addressing your contact as "Dear" is very formal, and maybe overdoing it. Likewise, starting your email with "Hey" or "Howdy" is informal and implies a closer relationship than you may have. Find a middle-of-the-road, opener such as "Hello" or "Hi"
3. Introduce yourself
   This is especially important when making first contact. Before you move on to the rest of your email, give the contact your name, where and why you are writing them.  No one is open to providing information to complete strangers.
4. Stay on topic and to the point
   In our busy business world, people don't have time for a novel in their email.  Keep your email brief, to the point, and on topic.  Reference a previous conversation if you need to re-establish your relationship, and avoid anything unrelated to the topic at hand.
5. Avoid slang
   This should be self-explanatory, but you'd be surprised how often "professional" emails are filled with slang. If your contact needs to open the Urban dictionary to understand what you're asking, you're in trouble.
6. Proofread before sending
   This is another tip that should be self-explanatory, but we've all made this mistake. Especially when on the go, writing a quick reply on the phone and sending without thinking.  It's all too easy to make critical mistakes.  If you use an email client that has a delay/recall send feature, make use of it. It can save you a world of trouble.
7. Attachment Etiquette
   Attachments are the #1-way hackers try to access your computer, by embedding viruses.  Never send an unsolicited attachment, keep them small, and clearly named.  Email is meant for messages, not file transfer. If you have lots of files, or large files, use a file service such as Dropbox or Google Drive to ease the sharing of files.
8. Signature
   All professional emails need a detailed signature.  How you format it is up to you and to your preference, but the information included should be along the lines of.
   Your Full Name
   Job Title
   Place of business, with address
   Public facing phone #s
   Website & Social media links
   A inline image, business logo, headshot, etc.  This is a matter of some debate as they are attachments. (see point 7, Attachment Etiquette)
   All of the above of-course, should belong to the business.  No personal information or links. 
9. One-liners and getting the last word
   Were all tempted to send that last email just to say "Thanks" and we all know that person who always needs to have the last word. Try to avoid that temptation, sure your "thank you" message is nice, and polite.  But, on the other end is someone working hard, getting dozens, possibly hundreds of emails a day. If that last email doesn't require a response, just let it slide.
10. Don't get mistaken for spam
    This is a tricky one, with a ever growing list of every more complicated rules.

• Don't send unsolicited email
• Don't use all caps anywhere in your email or its subject line.
• Don't use video, Flash, or javascript within your email.
• Don't embed forms in your emails; send recipients to a landing page on your site instead.
• Don't use spam trigger words like "free," "guarantee," and "no obligation" in your subject line or email body. These are spam trigger words, and will see you junked. List of Spam Trigger Words
• Don't use a red font when drafting your email. Also do not use white font on top of a white background.
• Don't use exclamation points!!!!!
• Don't forget to use spell check; misspellings and bad grammar are yet another spam indicator in your email copy.
• Don't jam pack your email copy with search / marketing keywords.
• Do ask your contacts to whitelist you and add you to their address book. Spam filters are more aggressive than ever, and sometimes email people value still end up in spam boxes. By asking your subscribers to add you to their address book, it tells spam filters to back off.
• Do include a clear unsubscribe link(If this is a mailing list) and a physical mailing address in your signature block. If you are sending bulk-marketing email, a functional unsubscribe link is the law.
• Do include your recipient's name in the 'To:' field so spam filters know that you do, indeed, know your recipient. Use the address book in outlook properly, and this will be automatic.
• Do keep emails short; too much text is another red flag for spam filters.
• Do include the date somewhere in the body of your email to show your message is current.

Pro Emails