Fix Outlook and Office 365 issues

Exchange Online — Email Flow, Forwarding & Troubleshooting

This guide covers managing email flow in Microsoft 365 — setting up email forwarding, troubleshooting delivery problems, importing mailbox data (PST files), and using the built-in diagnostic tools to fix common Outlook and Exchange issues.

Email Forwarding in Microsoft 365

There are two ways to forward email in Microsoft 365. The method you use depends on whether the user needs to keep a copy of forwarded email.

Option 1 — Forward from the Microsoft 365 admin centre (recommended)

1. Sign in to admin.microsoft.com.
2. Go to Users → Active users and click the user's name.
3. Click the Mail tab.
4. Under Email forwarding, click Manage email forwarding.
5. Toggle Forward all email sent to this mailbox to On.
6. Enter the forwarding address.
7. To keep a copy in the original mailbox, tick Keep a copy of forwarded email in this mailbox.
8. Click Save changes.

Option 2 — Forwarding rules set by the user in Outlook

1. In Outlook (desktop or web), go to Settings → Mail → Rules.
2. Click Add new rule.
3. Set the condition to Apply to all messages.
4. Set the action to Forward to and enter the email address.
5. Save the rule.

Note: Microsoft 365 blocks automatic forwarding to external addresses by default (anti-spam policy). See the section below if external forwarding is being blocked.

Allow external email forwarding (admin setting)

1. Go to security.microsoft.com.
2. Go to Email & collaboration → Policies & rules → Threat policies → Anti-spam.
3. Click Anti-spam outbound policy (Default).
4. Under Automatic forwarding rules, change the setting from Automatic - System controlled to On - Forwarding is enabled.
5. Click Save.
6. Security note: Only enable this if your organisation genuinely requires it. External auto-forwarding is a common vector for data exfiltration by compromised accounts.

Troubleshooting Email Delivery Problems

Use the Message Trace tool

Message Trace lets you track exactly what happened to a specific email — whether it was delivered, filtered, or blocked.

1. Go to admin.exchange.microsoft.com.
2. Go to Mail flow → Message trace.
3. Enter the sender and recipient email addresses.
4. Set the date range (messages are traceable for up to 90 days).
5. Click Search.
6. Click on a result to see the full delivery report — including whether the message was filtered as spam, quarantined, or successfully delivered.

Common delivery failure reasons

Setting Up SPF, DKIM & DMARC

These DNS records prove your domain is authorised to send email and significantly reduce the chance of your emails being marked as spam.

SPF record

Add this TXT record at the root of your domain in cPanel → Zone Editor:

v=spf1 include:spf.protection.outlook.com -all

If you send from other services (e.g. a mailing list platform), add their include statements before -all.

DKIM

1. Go to admin.exchange.microsoft.com → Mail flow → DKIM.
2. Select your domain and click Enable.
3. Microsoft will display two CNAME records to add to your DNS. Add these in cPanel → Zone Editor.
4. Once DNS has propagated, return to this page and click Enable again to activate DKIM signing.

DMARC

Add this TXT record to your DNS (adjust the rua address to your own):

v=DMARC1; p=none; rua=mailto:dmarc-reports@yourdomain.co.uk

Start with p=none (monitoring only), then move to p=quarantine or p=reject once you confirm legitimate email is passing DMARC checks.

Importing a PST File into Microsoft 365

PST files are Outlook data archives. You can import them to migrate historical email into a Microsoft 365 mailbox.

Method 1 — Import via Outlook desktop (small PST files)

1. Open Outlook. Go to File → Open & Export → Import/Export.
2. Select Import from another program or file → Next.
3. Select Outlook Data File (.pst) → Next.
4. Browse to your PST file. Choose whether to replace duplicates or allow them.
5. Select the target folder (or import to the top of the mailbox).
6. Click Finish. The import runs in the background.

Method 2 — Network upload via the Microsoft Purview compliance portal (large PST files)

For bulk migration of large PST files:

1. Go to compliance.microsoft.com → Data lifecycle management → Import.
2. Click New import job and follow the wizard.
3. You will be given an Azure SAS URL to upload PST files using the AzCopy tool.
4. Once uploaded, map PST files to mailboxes using the provided CSV template.
5. Start the import job. Progress is shown in the compliance portal.

Fixing Outlook Connection Problems

Use the Microsoft Support and Recovery Assistant (SaRA)

Microsoft's free diagnostic tool automatically detects and fixes many common Outlook and Microsoft 365 problems.

1. Download the tool from aka.ms/SaRA-OutlookSetup.
2. Run the installer and open the app.
3. Choose the scenario that matches your problem (e.g. Outlook → Outlook keeps asking for my password).
4. Sign in with your Microsoft 365 credentials when prompted.
5. The tool will run diagnostics and attempt automatic fixes, or guide you through manual steps.

Outlook keeps asking for a password

• Ensure Windows Credential Manager is not storing an old/incorrect password: open Control Panel → Credential Manager → Windows Credentials and remove any entries for Office or MicrosoftOffice.
• Check that your Microsoft 365 account is not blocked: admin centre → Active users → confirm sign-in is not blocked.
• Run the SaRA tool (see above) — it specifically diagnoses this issue.

Outlook profile is corrupted

1. Go to Control Panel → Mail (Microsoft Outlook).
2. Click Show Profiles → Add and create a new profile name.
3. Click Add an account and follow the wizard to add your Microsoft 365 account.
4. Set the new profile as the default and restart Outlook.

Calendar sharing not working

• Confirm both users are in the same Microsoft 365 organisation.
• The calendar owner must explicitly share their calendar: in Outlook, right-click the calendar → Share → Share Calendar → enter the recipient's email → choose permission level → Send.
• External calendar sharing requires the admin to enable it: admin centre → Settings → Org settings → Calendar → allow users to share calendars with external users.

Related Guides

• Basic mailbox settings for Outlook and other email clients (POP/IMAP)
• Diagnostics log collection in Support and Recovery Assistant
• Add an Outlook.com or Office 365 account
• How to Create Email Account in the Control Panel
• Groups naming policy

Need Help?

Need help setting this up? We can manage your Microsoft 365 for you — from setup to ongoing support.

Find out more about our Microsoft 365 managed service →