1. Yes, you will be able to link your Office 365 email accounts to the ONLYOFFICE Mail module.
2. Please, note, that ONLYOFFICE Mail gives you an opportunity to link a thread or a single message to a CRM element with the purpose to transfer all the necessary information about the contacts, cases, opportunities sent by email to your CRM module. To lean a visual and detailed instruction about how to integrate Mail module with CRM module, please, follow this link:http://helpcenter.onlyoffice.com/gettingstarted/mail.aspx
(>> Integrating with CRM).
3. Please, note, that if you connect using IMAP and the server doesn't disallow the sending of emails, in this case all the folders will be downloaded (except the foders "Drafts" and "Trash"). If you connect using POP3, in this case the folder "Inbox" will be downloaded only.
4. Please, note, that ONLYOFFICE Mail allows you to add a signature to your email messages. To learn a visual and detailed instruction about how to work with the Mail module and add a signature to the email message, please, follow this link:http://helpcenter.onlyoffice.com/gettingstarted/mail.aspx