Re:Making email more modern with JMAP
by marcosdumay on Sunday August 18, 2019 @01:07PM
(#20731419)
If you are talking about SMTP, servers may fail on receiving any character larger than 127, unless the client started the session with EHLO and the server announced either the 8BITMIME or the BINARYMIME extensions, where the first one only allows valid UTF8 stings, and the second requires a completely different mechanism that does not use DATA.
The only significant characters in email are carriage return, line feed, and period. There's also a line length limit in the SMTP protocol specification. Other than that, bytes sent during the DATA phase are sent unaltered.
Base64 encoding is meant to address this, but it results in a 33% overhead in attachment size. On the usenet side, people came up with an encoding scheme called yenc that actually only escapes those characters mentioned above and only as a 2 to 3% overhead over the original file size.