`user.js` settings I use:

|| '''Setting''' || '''Value''' || '''Rationale''' ||
|| font.size.systemFontScale || 100 || Default font scale ||
|| mailnews.wraplength || 0 || Disable text wrapping in composer ||
|| mail.strictly_mime || true || Use base64/quoted-printable only, do not use 8bit/7bit encoding. [[https://forums.zoho.com/topic/zoho-break-dkim-signatures-body-hash-if-8bit-encoding-are-used-through-smtp|Addresses a known problem with Zoho.com]]. ||

== Unknown settings ==

I had these set at one point or another, but I don't quite understand what they do.

 * `mail.compose.default_to_paragraph`

== Composer window line-height ==

In omni.ja:chrome/classic/skin/classic/messenger/messageQuotes.css:

{{{#!highlight css
/* workaround for MS Outlook mails where the line-height is set to 0 */
body {
  line-height: initial !important;
}
}}}