The "Report a Security Issue" form is broken


The “Report a Security Issue” (Report a Security Issue | Yii PHP Framework) seems to be broken.
After filing a report I received the following email:

Subject: Undelivered Mail Returned to Sender

This is the mail system at host *****.

I’m sorry to have to inform you that your message could not
be delivered to one or more recipients. It’s attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

The mail system

<*****>: host[2a00:1450:400c:c03::1b] said: 550-5.7.26 This
mail has been blocked because the sender is unauthenticated. 550-5.7.26
Gmail requires all senders to authenticate with either SPF or DKIM.
550-5.7.26 550-5.7.26 Authentication results: 550-5.7.26 DKIM = did not
pass 550-5.7.26 SPF [] with ip: [2a01:4f8:172:16b0::a:6] = did
not pass 550-5.7.26 550-5.7.26 To mitigate this issue, please visit
Gmail’s authentication guide 550-5.7.26 for instructions on setting up
authentication: 550 5.7.26

f4-20020a5d6644000000b003232009d578si4116259wrw.243 - gsmtp (in reply to
end of DATA command)

[**** = content anonymized for forum]