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What is HTML e-mail?
Information about MIME types
HTML mail for older AOL clients
HTML e-mail is used to bring life to e-mail communications. Originally, e-mails
were restricted to plain text; now, new e-mail programs allow users to see more
vibrant and dynamic content. These e-mails can now include colors, links, and
images, making them as attractive and visually stimulating as web pages.
HTML e-mails are created by including HTML tags into the body of the e-mail and
then inserting a special MIME type that tells the program to render the content
according to HTML rules. It's important to include the MIME type;
without it, the e-mail is displayed in plain text only, and the HTML tags become
visible to the reader.
MIME stands for Multipurpose Internet Mail
Extensions. MIME types are used to send non-ASCII information, and this is
what allows e-mail programs to realize that it's an image instead of a garbled
series of characters.
MIME types are specified in the header of the e-mail, which is where the
program also finds the "To", "From", and other display or encoding
information. Typically, when an e-mail is sent, it includes the line
Content-Type: text/plain
This notifies the program that a plain text e-mail has been received. To
send HTML e-mail, the Content-Type should be modified. Depending on the
situation, one of the following will be used:
Content-Type: text/html
Content-Type: text/x-aol
Most HTML e-mail capable programs understand the first Content-Type, including AOL 6.0. Older versions of AOL, however, require the second
Content-Type to be used.
Does an e-mail program support everything? Not at all.
These e-mail programs are often only able to do a simplified amount of
rendering. They certainly are not able to perform on the level of your average
Internet Explorer or Netscape browser.
One reason is because of the security hazards involved with sending
HTML e-mails. These e-mails can expose the unwary user to hostile viruses or other
intrusive programs. Starting with the AOL 6.0 client, the e-mail program
will render nearly all HTML tags but will exclude several pieces of
functionality typically found on websites.
- Scripts (e.g.. JavaScript, VBScript)
- Java
- Frames and IFrames
- Tooltips
- Active X
- Video
- Audio
- External Style Sheets
- Meta Refresh
The common theme here is end-user security. Malicious e-mailers can bury
a wide variety of harmful actions within the HTML e-mail, including programs that
activate upon download. Also, as is the case with Meta Refresh, a
user can be sent to another web site automatically. It
is important to AOL that the end-user be protected from these potential security
hazards.
On AOL clients older than 6.0, the MIME header should be MIME/X-AOL.
This allows the e-mail to be translated using AOL's Rich Text Format. RTF
is not as full featured as what is available from AOL 6. HTML tags that are not supported by RTF will be displayed as plain text. Additionally, no
tables are supported. Users should be careful to only use the
following tags when sending HTML e-mail to clients older than AOL 6.
| BREAK: |
BR |
| FONT: |
FONT |
| BOLD: |
B |
| ITALICS: |
I |
| UNDERLINE: |
U |
| SUBSCRIPT: |
SUB |
| SUPERSCRIPT: |
SUP |
| BIG: |
BIG |
| SMALL: |
SMALL |
| HEADER: |
H1, H2, H3 |
| PARAGRAPH: |
P |
| BODY: |
BODY |
| HYPERLINK: |
A |
| CENTER: |
CENTER |
| STRONG: |
STRONG |
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