feat: Web UI improvements

[soulteary]

The purpose of this issue is to collect and organize the next improvements to the interface.
If you have any suggestions, please leave your voice here.

• email filter support: feat: allow filtering of emails in http endpoint #334
• bcc support and ui update: any plan to support bcc? #233 Feature Request - Dispaly From Email Address #363

[san-chang]

• feat: Pagination support on mail list #392
• Group emails by to #43

[KillenX]

What do you think about adding an option to disable or discourage clearing the inbox? If one would like to use maildev as an archiving tool, for example.