Gmail provided by the paid Google Workspace service (formerly known as G Suite and Google Apps) has unofficial DNSSEC-signed MX records available for use. The officially supported ones that you’re told to configure do not offer DNSSEC signing.

These MX records have both IPv4 and IPv6 addresses, although the records are not officially supported or documented and may be unreliable or removed at any point. (I’ve been using them for a while now and they seem perfectly fine to me but use at your own risk.)

mx1.smtp.goog
mx2.smtp.goog
mx3.smtp.goog
mx4.smtp.goog

The table below has the MX record and the A and AAAA record values.

mx1.smtp.goog
    216.239.32.151
    2001:4860:4802:32::97

mx2.smtp.goog
    216.239.34.151
    2001:4860:4802:34::97

mx3.smtp.goog
    216.239.36.151
    2001:4860:4802:36 …