When did MIME get introduced?
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MIME (Multipurpose Internet Mail Extensions) was introduced in the early 1990s through RFC 1341, later updated as RFC 2045. That's when email stopped being text-only and gained the ability to carry attachments, images, video, and characters from any language.
Before MIME, sending a file via email meant encoding it manually with uuencode, pasting the resulting wall of gibberish into your message, and trusting the recipient to decode it back into a usable file. MIME automated that entire process and made it invisible to users. Attach a PDF, hit send, done.
MIME is why modern email works the way it does. It's the reason you can send a logo in your signature, include an invoice attachment, or build an HTML email with embedded images. Without MIME, email would still be plain text paragraphs with no formatting, no attachments, no modern marketing campaigns.
And if you've ever wondered why HTML email took off in the late 1990s, MIME was the foundation that made it possible. Plain text could become formatted content, single-column messages could become multi-column designs, and newsletters could look like magazines instead of memos.
For deliverability, MIME matters because modern spam filters analyze MIME structure. A properly formed MIME message signals professionalism. A malformed one (missing headers, broken encoding, mismatched content types) raises flags. Most ESPs handle MIME for you, but if you're building custom email systems or debugging delivery issues, understanding MIME structure helps you spot what went wrong.
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