email: Attempt to suppress email auto-replies.
email: Attempt to suppress email auto-replies.

This applies a commonly-used, though non-RFC, header which suppresses
auto-replies to the message.  There is a small chance that this will
result in bad filters thinking the messages *from Zulip* are
themselves auto-replies, but this seems a small risk.

Fixes: #13193.

rht/zulip,andersk/zulip,andersk/zulip,rht/zulip,zulip/zulip,andersk/zulip,andersk/zulip,andersk/zulip,andersk/zulip,rht/zulip,zulip/zulip,zulip/zulip,zulip/zulip,rht/zulip,rht/zulip,andersk/zulip,zulip/zulip,zulip/zulip,rht/zulip,zulip/zulip,rht/zulip