Cannot send email to reportphishing@apple.com

Attach the phishing email to your email to reportphishing@apple.com rather than forwarding it.

From: Phishing & Other Suspicious Emails

"Forwarding the message with complete header information provides Apple with important information. To do this in OS X Mail, select the message and choose Forward As Attachment from the Message menu. For other email applications or webmail based services, consult your provider’s support information to determine how to forward messages with complete headers."

Hey Ed!

You are correct that the contact to report phishing emails purporting to be Apple is reportphishing@apple.com. Based on the error, it seems to be an anti-spam message. This is not something I have great experience with, nor do I have the resources and diagnostic tools to more closely analyze the issue. I'd say the best way to resolve this is by contacting your email provider (Apple Support if it is an iCloud address) and seeing if they can help. You could also try reporting it to their non-phishing abuse email at abuse@icloud.com. This wouldn't be as ideal, but it's going to the same people.

Sorry I am unable to provide a better answer for you, but I hope this helps. Thanks for taking the initiative to report those scammers!