Soft bounce sends a 421 error to the sender, meaning temporary
failure. Soft bounce is not supported as a user-settable option.
The filter simply filters your forwards list to make it easier to find
an existing forward without having to scroll the page. To use it,
just start typing into the filter and the forward list will shrink to
show only matching items. The filter matches on alias, forward, and
memo. The filter supports regular expressions. eg, ^def would match an
alias 'defghi', but not 'abcdef'.
No Rewrite" refers to the rewriting of email headers (mainly
"Reply-To") in inbound
mails, which allows masking of your real address when you reply. The
rewritten headers sometimes caused overzealous spam filters to reject
the mail. The main example was Paypal or eBay email forwarded to
Gmail.. In the latest release, we automatically suppress the header
rewrites for those specific cases. However some users prefer to
disable header rewrites anyway (eg their email client handles address
masking) so the option is back.