Microsoft Article:

Enable or disable authenticated client SMTP submission (SMTP AUTH) in Exchange Online

1. Set up a "catch-all" mailbox

Since Chronicle can only POP from one email address there needs to be a generic box that is NOT used by any user to gather all email. Ex: mailbox@yourdomain.com. This mailbox needs to allow POP access.

2. Forward all the individual boxes to the catch-all

All emails that are delivered to individual@yourdomain.com needs to forward to the account chronicle is retrieving from, mailbox@yourdomain.com

Chronicle uses the X-Header of the email to determine the original recipient and deliver it to the appropriate individual.

3. Give the catch-all send as permissions

Since the SMTP application for Chronicle will be sending all emails to the catch-all address, it needs to have send as permissions for each individual user.

Example: incoming email is to amy@yourdomain.com, this forwards to mailbox@yourdomain.com and is retrieved by Chronicle. When Amy replies to the message she is sending from amy@yourdomain.com and the mailbox@ account needs permissions to send as this user.

4. Configure the Main System Setup in Chronicle with the catch-all mailbox settings

It will need the email address, password, POP address, and SMTP address. For SSL/TSL encryption check the box to enable.

NOTE: BCC emails will not be delivered into Chronicle inboxes. Tierra.net creates custom X-headers for inbound emails (requested by Chronicle years ago) that stores BCC information so that Chronicle can deliver the messages. Most other email providers do not provide this X-header support. Without the BCC information in the X-header Chronicle does not know who the email is to.