Frequently asked questions about Exchange Online mail and Outlook in business tenants.
Mailbox and storage
How big is a mailbox?
Default quotas depend on plan (often 50 GB or more on business plans). Shared mailboxes have separate limits.
Can I increase one executive mailbox?
Admins can adjust quotas within plan maximums or archive to another location.
Mail flow and DNS
What DNS records do I need?
At minimum MX to Microsoft, plus SPF and increasingly DKIM/DMARC for deliverability.
Can I forward all mail to Gmail secretly?
Transport rules can forward, but hidden forwarding is a security risk—review after incidents.
Migration
How long does cutover take?
Small tenants: a weekend DNS switch with staged mailbox sync. Larger tenants: phased batches.
Can we run Gmail and Microsoft in parallel?
Yes with coexistence or dual delivery short term; plan end date to avoid split inboxes forever.
Clients and auth
Why did my scanner stop sending mail?
Many devices used basic auth; use SMTP relay or authenticated connectors instead.
Does Outlook need a VPN?
No for standard cloud mail; some regulated firms add network controls separately.
Calendar
What are room mailboxes?
Resource accounts for booking meeting rooms and equipment.
Can I share calendars externally?
Yes with policies; default is often internal-only for privacy.
Pricing and setup
Mailbox counts drive subscription cost. See pricing or M365 Deals for SKU fit.
