Please add functionality to configure general email filters in Plesk.
The same functionality is implemented in cPanel:
https://documentation.cpanel.net/display/CKB/How+to+Configure+Mail+Filters

There is a Mail Importing feature in Site Import extension, but it is possible only to migrate emails one by one. It would be great if there is an ability to migrate a couple of mailboxes at once.

I would be a good Idea to be able to change webmail URL via Plesk, not using workaround https://support.plesk.com/hc/en-us/articles/213947325-How-to-set-up-an-access-to-webmail-over-mail-example-com

There is White List under Tools & Settings > Mail Server Settings, it is used by SpamAssassin.

MailEnalbe has also White List under Servers > localhost > Services and Connections > SMTP > Properties > Whitelist.

MailEnalbe Whitelist cannot be managed through Plesk.

It would be nice, to have ability to manage MailEnalbe Whitelist in Plesk interface

When installing Plesk with SmarterMail, the mailbox usage stats are calculated, however, the mail traffic usage stats (IMAP/POP3 + SMTP) are not calculated.

It would be really useful that Plesk would calculate mail traffic usage for when SmarterMail is being used, otherwise, we cannot monitor the traffic usage made by our customers nor limit it.

Hello,

Please add functionality to create webmail account in Plesk if an external SMTP server is configured:

https://docs.plesk.com/en-US/onyx/administrator-guide/mail/using-plesk-without-the-mail-server.72346/

Add alert tag to message body for external emails:
The tag can be " CAUTION ! This email originates from outside the organization "

In order to comply with RFC3834 the auto replay function should consider the X-Auto-Response-Suppress header. Also not replaying to mail with Auto-Submitted: auto-generated would be nice.

Hello,

Please add the possibility to purchase an extended license for mail servers with Plesk.

It would be helpful if I prefer to separate my mail services from my main hosting.

Any kind of wildcard mail aliases (regex and/or /?) would be highly appreciated in order to realize a "allow form all but anything like..." handler. Example: Ban all info-@domain addresses.

I had somenting similar at my old provider but not with new one using plesk. Now I need to insert dozens (hundreds) of addresses one by one...

If there is already a way to realize something similar I was not able to find it (or my provider did not enable it)...

It would be nice to provide mail SSL/TLS support with SNI for more domains from single IP

Implement feature to configure mails sent to domain hosted in Plesk be delivered to external mailserver if mailbox does not exist in Plesk.

Hello,

It would be amazing to be possible to create a distribution list via Plesk Premium email without creating a mailbox and forward the emails.

eg. create a example@example.com without a mailbox and forward to a group RH or Sales.

Add a functionality that notifies a sender through an email notification that his sent email has been deferred within 30 minutes

the gdpr request to change password every 6 month. it would be nice every 6 month remember to client to change password.
witha link to a dedicate page to change pwd ( out webmail ) and with captcha or other security system.

When DKIM is activated, the key isn't added when you use the PHP mail() function, for example if you have a contact form on the website. Please add because this generates false SPAM-detection problems. Google for example thinks it's strange that sometimes the DKIM key is added and sometimes not. Please keep in mind that this should work with an external DNS-service too.

Currently the only way to get the DKIM key is to decode the private key from the shell when using an external DNS service, however it would be nice if the public key is just being displayed in the web interface so the user can see it and add it to the external DNS.

Include Horde webmailer's internal data in backups done with Plesk Backup Manager

Implement Dovecot LMTP.
Currently LDA is used for mail local delivery.
LMTP has a better performance and using it allows to avoid "Inotify instance limit for user (UID popuser) exceeded, disabling. Increase /proc/sys/fs/inotify/maxuserinstances" issues.

https://workaround.org/ispmail/jessie/postfix-dovecot

Right now spf hook checks incoming mail for all domains if it is enabled in Tools & Settings > Mail Server Settings.
There is no simple way to disable it for some domains/subscriptions that may not need it present.