When an email was received through the Plusnet system, there was an email heeder of Envelope-To which contained the real email address that the email was sent to, taken from the Envelope data. This is not the same as the contents of the To header. I have used the Envelope-To data here in my email client to filter the email into its correct location for 30 years!
It seems that after migration the Greenby system does not currently provide an Envelope-To header, but instead provides a Delivered-To header. However this contains the mailbox address that the email was delivered to, which is NOT the email address. This has resulted in emails not being filtered locally to their correct locations, despite being assured that no changes would be required.
I have noticed that Greenby does have a new additional non-standard header X-Original-Recipient, which seems to contain the actual email address from the Envelope data. However, my email client cannot filter on this non-standard field.
Note that the mailbox concerned has over 70 aliases for the mailbox, so it is totally impractical to create a mailbox for each address.
I have asked Greenby if the Envelope-To header be re-instated to be like Plusnet, as we were assured.
While I await a response, I am posing here in case others are also affected.
