Google says 500-ish for JS: https://developers.google.com/closure/compiler/faq#linefeeds
The Closure Compiler intentionally adds line breaks every 500
characters or so. Firewalls and proxies sometimes corrupt or ignore
large JavaScript files with very long lines. Adding line breaks every
500 characters prevents this problem.
uglify --max-line-len 500 or grunt-contrib-uglify options: { maxLineLen: 500 }
I'm not sure if the limit applies to HTML or CSS, but I haven't seen that option for any CSS compressor I've used.
SMTP rules would apply to HTML email:
https://www.ietf.org/rfc/rfc0821.txt
The maximum total length of a command line including the command word
and the CRLF is 512 characters.
