Groupware requirements for the organization

Hi All,
We would like to know if the following requirements are met in the Nextcloud. Can somebody please comment on it?

Infrastructure is private (not in the Cloud)
Preferably on Linux OS
Setup signature banner for everyone for a specific time period (from-to-date)
Setup individual signatures (same signature on all devices: mobile, desktop, tablet…)
Setup individual calendars (synched on all devices: mobile, desktop, tablet…)
Check availability for other accounts in the organization
Organize meetings with accounts in the organization and outside the organization
Send notifications and reminder for appointments
Reserve cars and meeting rooms in the same manner as meetings with people
Allows for delegates (ie. secretary can manage meetings for manager)
Import organization contacts for all accounts
Share account contact (personal and organizational) between all devices
Easily add account contact from received email
Create and share tasks for people in the organization
Account properties
Easily change surnames for accounts
Easily verify qoutas and notify about quotas limitations
AD connectivity
Synch mail accounts with AD accounts
Out of office
Setup/edit/turn off and on HTML out of office from all devices : mobile, desktop, tablet…
Desktop application
Supports Thunderbird and occasional Outlook
Easy one time migration of our existing 331 IMAP accounts to the new system
Webmail solution to use from home
Enables access to (all – also archived) email, calendar, contacts
Anti-spam, Anti-virus, Sieve filtering
Allows for all of the above
Allows for easy backup and restore of mailboxes (ie. when users deletes messages or tasks or calendar events and wants them restored from backup)
Allows encrypting emails with sensitive information (ie. patient personal information that doctors within the organization share) with public certificates

Nextcloud does not provide a mail server, however you have an integrated webmail client (the mail app) which is probably still lacking some of the features you are asking (encryption, …). However for mail there are probably existing solutions to use an existing AD (not within Nextcloud) and use the same AD for Nextcloud authentication.

The other things are mostly available, though some small features (organize meetings in the calendar app) are still missing. If you have resources on your own, or with an enterprise subscription, this shouldn’t be too difficult to implement.

Perhaps ask enterprise support, it’s possible that they already have experience with similar setups and with everything integrated, it could be a good idea to rely on support.