On 14 June 2019 04:25 @lbutlr via dovecot < dovecot@dovecot.org> wrote:

Well, progress. At least now editheader loads. Sadly that brings up new errors.

specified field name `Reply-To:' is invalid.

if header :contains "List-id" "<users.spamassassin.apache.org>" {
addheader "Reply-To:" "<users.spamassassin.apache.org>";
addheader "X-added-reply-To:" "True";
fileinto :create “spamassassin";
stop;}

Have you tried "Reply-To”?