Most of the time all they see is the actual HTML code behind the message. Any of these can cause trouble with HTML (or non-text attachments). While this makes your email interesting and pretty to look at, it can cause problems for other people who receive your email because they may use different email programs, different computer systems, and different application programs whose files are often not fully compatible with each other.
This makes URLs into clickable links and it means that graphic images, formatting, and color-coded text can also be included in email messages. Many email programs, usually the mail programs that come with browser packages, allow users to include attachments or HTML/Rich Text within their email messages.Why not send list mail in HTML/Rich Text or include non-text Attachments (MIME)? Turning Off HTML/Rich Text and Attachments in email client programs.Why and How to Send List Mail in Plain Text
