Received-SPF: softfail (google.com: domain of transitioning [email protected] does not designate XXX.XX.XXX.XXX as permitted sender) client-ip=XXX.XX.XXX.XXX; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning [email protected] not designate XXX.XX.XXX.XXX as permitted sender) [email protected]
SnapOverflow
If you are expecting your mail to be reliably delivered, then a soft fail is not good. Your message may still be delivered depending on the policy of the receiving system.
For the best chance of successful delivery you should update your SPF record so the message you are trying to send is permitted.