Why Are My Emails Showing Random Characters? Understanding Base64 and Quoted-Printable Encoding

By QuotedEncoder Editorial Team | Networking & Deliverability

If you have ever peered deeply into the raw source code of an email, or if you're a developer trying to build automated email-sending APIs, you've likely encountered giant, unreadable blocks of letters resembling pure gibberish. This isn't a glitch, nor is it an encryption security mechanism against hackers. It is the fundamental architecture of the global email network known as MIME (Multipurpose Internet Mail Extensions) encoding.

In this guide, we break down why modern emails cannot be sent as "plain text" over the internet, and what exactly happens when a subject line containing an emoji is translated via Base64 or Quoted-Printable syntax strictly natively.

The Origin of the 7-Bit Problem

Origins of the 7-Bit Limitation

The problem originated with RFC 822 (1982), which defined the standard for ARPA Internet Text Messages. Email was designed to use 7-bit ASCII characters—meaning only 128 possible values (0-127), with the high bit (8th bit) stripped or ignored

This limitation existed because:

Early network equipment (modems, multiplexers, terminal concentrators) was hardware-limited to 7-bit communication
The Simple Mail Transfer Protocol (SMTP), defined in RFC 821, was built on this assumption
Control characters in the 8-bit range (128-255) could be interpreted as commands or stripped by intermediate systems
Line length was also restricted to under 1000 characters

Why This Became a Problem

As computing evolved, users needed to send:

Binary files (images, documents, executables) containing 8-bit bytes
International text with accented characters and non-Latin scripts
Rich content beyond plain ASCII text

When 8-bit binary data passed through 7-bit-only systems, it became corrupted—either by having the 8th bit stripped or by control characters being misinterpreted as protocol commands