Learn · email signature glossary
TL;DR
MIME stands for Multipurpose Internet Mail Extensions, defined in RFC 2045 through 2049. Email was originally limited to plain ASCII text; MIME extends it by defining content types and encodings, so a single message can carry an HTML body, attachments, embedded images, and text in any language. The structure that matters most for signatures is multipart/alternative: the message contains both a plain-text part and an HTML part, and the recipient's client picks which one to display.
Re: In practice
MIME is the reason an HTML signature can exist, and also the reason it sometimes vanishes. When a client shows the plain-text alternative (by user preference, on some watches and terminals, or in certain security gateways), your formatted signature is replaced by whatever sits in the text part, which is often nothing or an auto-generated fallback. Well-behaved sending setups keep a plain-text version of the signature in sync with the HTML one. MIME also explains embedded versus hosted images: a logo can be attached inside the message (referenced by Content-ID) or fetched from a URL, and hosted images are generally the safer choice because attached ones inflate message size and can appear as paperclip attachments in Outlook. Understanding the multipart structure makes most 'my signature looks wrong for one recipient' mysteries solvable.
Fwd: Worth a look
what BIMI is
BIMI is a DNS-based standard that displays your verified logo next to messages in the inbox. Learn its requirements, including DMARC and a VMC.
DKIM signing
DKIM adds a cryptographic signature to outgoing email that receivers verify against a public key in your DNS, proving the message was not altered.
what DMARC does
DMARC is a DNS policy that tells receiving mail servers what to do when a message fails SPF and DKIM checks. Learn how policies and reports work.
signature generator definition
An email signature generator is a tool that turns your details into ready-to-paste, email-safe HTML, sparing you from hand-coding tables.
what an HTML signature is
An HTML email signature uses markup to add formatting, images, links, and brand colors to your sign-off. Learn how it differs from plain text.
inline styles in email
Inline CSS puts style rules directly in each HTML tag's style attribute. Gmail and other clients strip style blocks, so email depends on it.
Free generator, no account required. Works in Gmail, Outlook, and Apple Mail.
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