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[ietf-smtp] Compressing SMTP streams

2016-01-28 15:42:44
Has there been any previous discussion on having a COMPRESS like extension
for SMTP?

Similar to RFC 4978 for IMAP.

I was hoping we could get this for free with TLS, but few libraries
implement it and seems to have made
them leary about it.  I don't think SMTP is implicated because it doesn't
use cookies/etc, but anyways.

There seems to have been some discussion ~13 years ago, but it went no

As for my reasoning, at least for us:

1) CPU is cheaper than bandwidth
2) message sizes are increasing, but base64 isn't going away

Theoretically, switching to some combination 8BITMIME, CONTENTBINARY and
BDAT, we'd save nearly as much bandwidth since a good fraction of the
compression is going to be recovering the base64 encoding overhead on
attachment types that aren't likely to compress much.  That said, with the
advent of DKIM, we can't easily change the encoding of messages without
breaking signatures, so we're kind of stuck using base64.

DKIM and ARC are also leading to larger headers, which should compress
relatively well, not to mention larger HTML text parts.

Of course, email is only a fraction of modern networks, but the overall
volumes at medium to large esps would still make a useful reduction.

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