Yahoo mail from web account adds content ID with suffix @yahoo.com, which when forwarded from mail clients gives error
When a web @yahoo.com account sends a mail with attachment, it adds a Content-Id: email@example.com field.
When this mail is forwarded from an iPhone or Android phone, it attaches another field within the content type field in mail header.
that header key added by iPhone is x-apple-part-url="firstname.lastname@example.org"
When this header key is read by some mail servers, they treat it as a content type .com and reject the mail.
It is requested to correct the Content ID field inserted by @yahoo.com web account when sending an attachment.