Make separate limits on Mail and Web disk spaces, so that hoster could sell one limit for web (i.e. 2Gb) and another limit for mail (i.e. 10x2Gb mailboxes)

Resellers should be able to configure the "Email Notifications" (http://download1.parallels.com/Plesk/Doc/en-US/online/plesk-administrator-guide/index.htm?fileName=59422.htm) like the admins, so they can have a whitelabled Hosting, independet from other Reselles and the Admin. Otherwise, all Clients, from different Reselles, get the same email.

In addition to that, a HTML Support, the Subject and the sender (email from) should be able to edit by each reseller, or by those, who have the permissions to do that.

Thanks for your attention

There should be a "Monitor only" Option at the Outgoing Mail Control to get Statistics about how many Mails are sent through Subscription/Domain/E Mail Address without actually limiting ...

ARC solves some problems of DMARC and should be implemented as well

According with RFC 8058 "Signaling One-Click Functionality for List Email Headers" (https://tools.ietf.org/html/rfc8058) in order to use the header "List-Unsubscribe" this must be included on "h" tag of DKIM sign, nowadays only "From:To:Subject;" are included on DKIM-Signature.

The idea is to allow the option to include additional information on the Plesk generated "DKIM-Signature" "h" tag.

A public list of all banned ip addresses in the customers workbench for a simply error check on customers side.

Sometimes blocked a single bad configurated client all other users on the same network.

So can the customers admin check in the own ip blocked.

I'd be great if you could configure that Plesk looks in Active Directory for users of a specified group and fetch their email adresses to create these

So it is not needed to have a domain resolving to any DNS in order to access the webmail.