Emails can be composed as HTML or plain text messages. HTML emails mainly offer the advantage of better formatting options over plain text emails. It is for instance possible to add bold or underlined text, lists or images. HTML emails on the other hand are considered a security and privacy risk. It is for instance possible to embed an - often 1x1 pixel image - in the HTML email to track if the recipient has read the email. There have also been cases where maliciously modified objects were included in emails.
The Thunderbird email client supports both plain text and HTML emails. The account settings hold the default preference for each email account in the mail client. This only affects email messages that are created in Thunderbird, not messages that are received.
The preference for incoming emails is found under View > Message Body As. Here it is possible to switch from the default Original HTML to Simple HTML or Plain Text.
This preference is valid for all incoming emails, regardless of the email address they have been sent to.
If you choose View – Message Body As – Original HTML, then you see HTML messages in their original form, except that:
* For privacy reasons you can choose not to allow messages to download remote images.
* Some messages might contain non-standard HTML that Thunderbird does not support.
For privacy settings, choose: Options (Preferences) – Privacy – General
Note: There are normally no security issues when you read a message in Thunderbird. It is not normally possible for hostile code to attack your computer just because you read a message. But if you open an attachment, then Thunderbird passes the attachment to your operating system or to some other application. Your operating system or the other application might allow the attachment to attack your computer.
If the message is plain text, then you always see plain text.
If you choose View – Message Body As – Plain Text, then you see plain text even if the message is really HTML. If the message is multipart, then you see the plain text part. Otherwise Thunderbird converts the HTML message to plain text.
Thunderbird normally enhances plain text by supporting certain HTML-like features:
- Bold, italic and underlined text.
- Smileys displayed as images.
- Attached images displayed in the body of the message.
- Links displayed in blue, and underlined.
- Flowed paragraphs (if the message was sent using flowed paragraphs)
- Quoted paragraphs outlined with colored bars (if the message was sent using flowed paragraphs)
- Signatures displayed in gray.
The supported smileys are:
:-) :) smile
:-( :( frown
;-) ;) wink
:-P ;-P tongue
>:o >:-o yell
It sometimes may be necessary to write HTML emails and plain text emails, depending on the recipient. While it is possible to switch the format in the account settings, it is possible to make a temporary switch when composing emails.
Holding down the Shift key before clicking on create a new message, or one of the reply options, switches from the default writing mode to the other.
Thunderbird will automatically display the plain text email editor if HTML emails are the default, and vice verse if the Shift key is pressed.
The composition window will display HTML elements like bold or underline if an HTML message is composed, or no text formatting options if it is a plain text email.
Holding down the shift key is the fastest way of switching between HTML and plain text composition windows.
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