Receiving an HTML Email Message from Outlook
Just because a recipient has Outlook doesn't mean that recipient will be able to see HTML-based email messages properly. To demonstrate this, let's compose the same HTML email in Mozilla Thunderbird and send it to an Outlook email address.
Again, here is a beautiful email, this time being sent to a recipient who is known to have Microsoft Outlook. Unfortunately, the recipient is puzzled when this email enters the Outlook Inbox. Here's what it may look like.
Here is an HTML message sent from a program other than Outlook and your email program does not support HTML even though the message was received in Outlook.
Reading HTML messages in Outlook
When a message comes in that makes Outlook seem as though it does not suupport HTML, a simple setting needs to be changed. In Outlook, click "File" and then choose "Options" from the menu on the left.
When the "Outlook Options" window opens, choose the "Trust Center" option and then click the "Trust Center Settings" button.
Next, click the "E-mail Security" button and then un-check the box next to the line that says, "Read all standard mail in plain text." This will turn off the setting that is causing Outlook not to display HTML-based email.
Now, click the "OK" button and then click "OK" again. Now, test to see if Outlook will display HTML mail by re-sending a sample.
Outlook HTML support being reactivated now allows the email to be rendered as the sender intended.
Image Credit (used inside sample email message): Wikimedia Commons/Ximonic, Simo Räsänen