When sending batch messages via e-mail, it would be nice to be able to italicise a section of the brand name that I intend to use. Is this possible? I'm aware that the context of a message can contain HTML, but I no information about whether communicating the MIME type of a header value is possible.

1 Answer 1


SMTP mail headers must be ascii characters. Sure you can write html using just ASCII characters, but mail clients will not render the content as html, at least not if they are properly written - allowing this would expose ALL sorts of vulnerabilities.

However the email subject can presented as base64 encoded UTF-8 which is supported by most clients, e.g. in PHP something like....


But bear in mind that security software may see this as you trying to deceive people, it will break the search on the MUA.

You can also ask the client to display a custom icon using BIMI.

  • Shame. Maybe JMAP will change this, since attaching a MIME type to each heading key would be relatively trivial then. Thanks for the clarification. Commented Jun 12 at 22:24

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