We regularly have problems when sending out HTML emails created ‘on the fly’ on a webpage postback. Various clients/users will get an email that does not display as expected, these display problems can never be recreated and the usual fix is to use plain text.

We stumbled upon the term ‘defang’ recently. Amongst other things, defanging means to ‘Render an email message or attachment harmless’, and is applied by Anti-Virus/email scanning software.

The only current problem with an HTML defanger, is that is can be too sensitive and may defang content that is not strictly HTML or non-harmful HTML. All text parts are scanned for HTML but this can be a complex issue since its hard to tell what the mail readers will interpret.

Anomy Sanitizer is an example of an email-scanner that defangs HTML.

The only safe option is use plain text, or use very basic HTML such as the <table> and <font> tags for every line of text – laborious but much more likely to get past the defanger!