The following message could not be forwarded to
destination@gmail.com for myemail
@email.com
Technical details of the failure:
5.7.26 This message does not have authentication information or fails to
5.7.26 pass authentication checks. To best protect our users from spam, the
5.7.26 message has been blocked. Please visit
5.7.26 https://support.google.com/mail/answer/81126#authentication for more
5.7.26 information. np9-20020a17090b4c4900b001dd67f12d27si173372pjb.106 - gsmtp
....
Many other mails are forwarded without any problem but one of them is blocked. What can I do in order to consider this email as safe ?