Email forwarding resulting in SPAM and bad headers

[sjw]

How can I circumvent spam errors when using a mail forwarder?

I have a domain which I have configured an email forwarder to forward all emails sent to

me@mydomain.com -> me@gmail.com

so all my emails land in my Gmail Inbox.

I am receiving emails from trusted external sources but they are going to spam more often than not AND the email address in Gmail shows

sender@senderdomain.com via mydomain.com

This also results in bad headers where it fails:

• Ok: SPF Alignment
• Failed: SPF Authenticated
• Failed: DKIM Alignment
• Failed: DKIM Authenticated

SPF: The sender (at sender.com) has a valid SPF record for his domain allowing for him to send from his server IP address BUT when it is forwarded, Gmail receives the email from my cPanel server IP (via mydomain.com) which causes an SPF mismatch.

DKIM: The sender server signs the message with the DKIM for sender.com. But when it is received in Gmail (via mydomain.com) it looks at the public DKIM for mydomain.com which of course results in a mismatch every time.

Is there anyway to fix this or is there a recommended workaround?