Corporate mail, task manager, file management?

Question

Email

Colleagues, good day! There was a question of reorganization of structure of work in the company.
Historically, company employees interacted through a single mail, parsing mail according to the rule (this came to me). Over time, such a system led to a collapse: hundreds of letters began to arrive daily, some of which employees “lose” without viewing due to volume, and management has to monitor and control the processing of letters.

In addition, there was a need for joint work on files, the organization of a certain database of documents: acts. invoices, purchases, etc., of course, all this needs to be organized with limited access.

Please tell me, perhaps a flexible corporate mail system, not very expensive (up to 20 people), with the ability to organize "some database" of documents with access profiling.
And ideally, as a cherry on the cake, so that management can view the "mails" from the "single window".

I would be grateful for tips and hints, maybe it will be an open source system - ready to install and maintain those. Thank you.

Answer 1

This is all Zimbra can do. However, if you attach scripts to hmailserver and post tasks in redmine, then it will also work fine,

Answer 2

Hm. I liked the idea about zimbra + redmine. Samba is included there, that is, there will be a file resource. If you do not need outlook - you can get by with the commuinty edition, if you need it - you will have to license the boxes, as far as I remember there in packs of 50 pieces.
To control mail, you will have to configure mirroring on the server. To mirror the sent letters, you may have to go into the settings of the mailer.