Do not send Out of Office reply for bulk or transactional emails

These auto-replies can cause further spurious email replies, or bounces from transactional senders that do not accept email.

While not foolproof, there are headers that indicate auto-replies or list server responses that could be discarded.

Precedence: bulk

Precedence: junk

Precedence: list

Auto-Submitted: auto-generated

X-List*

X-Mirror*

X-Auto*

X-Mailing-List

X-Auto-Response-Suppress: OOF

X-Auto-Response-Suppress: AutoReply

More on X-Auto-Response-Suppress:

https://docs.microsoft.com/en-us/openspecs/exchange_server_protocols/ms-oxcmail/ced68690-498a-4567-9d14-5c01f974d8b1

Some standards references:

http://www.iana.org/assignments/auto-submitted-keywords/auto-submitted-keywords.xhtml

https://tools.ietf.org/html/rfc5436

Zimbra also has a filter rule condition that references bulk/marketing emails, with “[Message] [is] [mass marketing (bulk)], and messages that would be detected by this rule should also not receive auto-responders.