550 SPF MAIL FROM check failed (Fail)

[crnunez]

Hello,
I have some Group List with this configuration:

Postoffice: mydomain.com
Mi email accounts: a1@mydomain.com, b1@mydomain.com

I have a Group as "0001G", this group has c1@mydomain.com for "To email to this group, use the email address below"...

Group Members:

any@otherdomain1.com
any1@otherdomain2.com
any..n@otherdomain..3.com

For the a1@mydomain.com email I have enabled redirect to c1@mydomain.com when new email arrive to this mailbox; then It should send to all group members.

ISSUE: Some email's are not delivered with this error: 550 SPF MAIL FROM check failed (Fail) this error appear on sender email.

*Sender* >>> to a1@mydomain.com >>> redirect to group members.

*Sender* has bounce email as 550 SPF MAIL FROM check failed (Fail).

Do you have why occurs this issue? Do you have any solution or tips?

I can detect that Mailenable try to send email to Member group as *Sender* but the sender is a foreign email account. Should MailEnable send through c1@mydomain.com?

Thanks!

[crnunez]

Someone has any idea?