Lab 07: Exchange Online and Internal Mail Flow

Overview

This lab continued the Microsoft 365 work completed in Labs 05 and 06. The existing @nietz.co.uk cloud user accounts and licensing baseline were used to validate Exchange Online mailbox readiness, shared mailbox administration, internal delivery, Send As behaviour, and message trace troubleshooting.

The lab is deliberately scoped to Exchange Online administration and internal mail flow. It does not claim external inbound mail routing, public MX changes, SPF, DKIM, or DMARC validation. Those records and external tests are reserved for Lab 08: External Mail Flow and DNS Records.

Objective

The objective was to complete practical Exchange Online support tasks: assign the correct admin role, confirm mailbox provisioning, create shared mailboxes, configure mailbox delegation, validate internal delivery, test Send As from the support shared mailbox, and confirm delivery using Exchange Online message trace.

Environment

Configuration and Evidence

1. Exchange Administrator Role Assignment

I assigned the Exchange Administrator role to the daily admin account so Exchange Online mailbox administration could be performed without relying on the setup/global admin account for routine support work.

Context: Delegated admin roles support least-privilege administration and reflect how routine Exchange tasks are normally separated from global tenant administration.

2. Exchange Admin Center Access

I opened the Exchange admin center and confirmed that the Nietz Ltd tenant showed Exchange Online administration areas including recipients, mail flow, roles, migration, organisation settings and troubleshooting.

Context: Exchange admin center is used for mailbox administration, shared mailbox configuration, delegation, mail flow and message trace.

3. User Mailbox Validation

I confirmed that licensed Nietz Ltd users had Exchange Online user mailboxes provisioned with @nietz.co.uk addresses.

Context: Mailbox provisioning depends on licensing and must be confirmed before Outlook, shared mailbox and mail-flow tests are trusted.

4. Shared Mailboxes Created

I created the [email protected] and [email protected] shared mailboxes. The Support mailbox also uses the helpdesk alias for a realistic service desk address.

Context: Shared mailboxes allow teams to manage common addresses without assigning the mailbox to a single named user.

5. Support Mailbox Permissions

I configured the Support shared mailbox with Send As and Read and manage / Full Access permissions for Chloe Bennett and Daniel Smith.

Context: Full Access allows a user to open and manage a shared mailbox. Send As allows a user to send messages that appear to come from the shared mailbox address. These are separate permissions.

6. Sales Mailbox Permissions

I configured the Sales shared mailbox with Send As and Read and manage / Full Access permissions for Kate Jones and Sam Jackson.

Context: Shared mailbox delegation is a common Microsoft 365 support task and is frequently checked when users cannot open a shared mailbox or cannot send as a shared address.

7. Internal Mail Flow Test to Support

I sent an internal test message from Emily Wilson to the Support shared mailbox and confirmed that the message arrived in the Support mailbox inbox.

Context: Testing internal delivery confirms that the shared mailbox can receive mail before moving on to Send As or external mail-flow scenarios.

8. Internal Message Trace Validation

I used Exchange Online message trace to confirm that the Lab 07 internal test message was received, processed and delivered to the Support shared mailbox.

Context: Message trace is a core Exchange Online support tool for investigating delayed, failed, blocked or misrouted mail.

9. Send As Support Test

I sent a message from the Support shared mailbox to Emily Wilson to validate that Send As worked from the user mailbox experience, not only from the admin permission screen.

Context: This validates the practical user-side result of the Send As permission assigned earlier in the lab.

10. Send As Message Received

I confirmed that Emily Wilson received the test message and that the message appeared as coming from the Support shared mailbox.

Context: Received-message evidence confirms the user-facing result: the recipient sees the message as coming from the shared mailbox rather than the delegate user.

11. Send As Message Trace Validation

I used Exchange Online message trace to confirm that the Send As validation message from [email protected] to [email protected] was delivered.

Context: This combines recipient-side Outlook evidence with administrator-side delivery validation.

Validation

The lab was validated when the Exchange Administrator role was assigned to the daily admin account, Exchange admin center opened with full admin navigation, user mailboxes were visible, Support and Sales existed as shared mailboxes, both shared mailboxes had Send As and Full Access permissions assigned, Support received an internal message, and message trace confirmed delivery.

The lab was further validated when the Support shared mailbox sent a Send As test message to Emily Wilson, Emily received the message as coming from Support, and Exchange message trace confirmed the Send As delivery.

No external inbound mail flow, public MX record change, SPF, DKIM, or DMARC validation is claimed in this lab.

Key Technical Outcomes

This lab demonstrated Exchange Online mailbox administration, shared mailbox creation, mailbox delegation, Send As permissions, internal mail-flow testing and message trace validation.

The lab also reinforced that Full Access and Send As are separate permissions: a user may be able to open a shared mailbox but still be unable to send as that mailbox unless Send As has also been granted.