- Outlook rules run on a person's computer, so city-based applicant routing built on them stops the moment that one always-on desktop is down or restarting.
- Exchange Online transport rules (mail-flow rules) live in the cloud and apply to mail regardless of whose computer is on, letting you retire the always-on machine entirely.
- A mail-flow migration is a good moment to right-size mailboxes: generic accounts become free shared mailboxes, and people lists become distribution groups or aliases.
- Send bulk and application-generated mail through a dedicated SMTP relay, not Microsoft 365, and pair any mail-flow change with correct SPF, DKIM, and DMARC records.
This spring, the office manager at a multi-branch staffing agency walked us through how applicant emails get sorted to the right branch. The answer made us wince: a single desktop in the payroll area, left on all day, running Outlook rules, and restarted by hand after every Windows update. "It is something I have to do manually," she said. When that one machine is down, applicant routing stops.
Client-side rules versus the cloud
The rules doing the sorting were Outlook rules, which run on a person's computer. Move that logic to the server and it runs inside Microsoft 365 itself, with no desktop required.
Microsoft 365 has Exchange Online transport rules, also called mail-flow rules. They live in the cloud and apply to mail as it passes through, regardless of whose computer is on. The city-based routing this company ran on one workstation (send applicants from this metro to that branch) is exactly what transport rules are for. Rebuild it there and you can retire the always-on machine entirely.
The tell that you have this problem: a computer nobody's allowed to turn off, doing a job no person actually does. Anytime business logic depends on a specific desktop staying awake, it belongs in the cloud instead.
A migration is a chance to tidy up
Moving mail flow is also a good moment to right-size mailboxes:
- Generic accounts like orders@ or applications@ can become shared mailboxes, which don't need their own paid license.
- Lists of people can become distribution groups, and second addresses for one person can become aliases.
That usually trims license spend and simplifies the setup at the same time.
Two things that quietly break email
While you're in here, two cautions that bite SMBs constantly:
First, don't send bulk or application-generated mail through Microsoft 365. Newsletters, automated notifications, and scan-to-email blasts should go through a dedicated sending service (an SMTP relay), or you risk your whole domain's deliverability.
Second, protect your domain reputation. Any change to mail flow should be made alongside correct SPF, DKIM, and DMARC records, the three DNS settings that tell the world which servers are allowed to send as you. Get them wrong and your legitimate mail starts landing in spam, or vanishing.
If your business runs on a rule, a script, or a routing step that lives on one machine in the corner, that's worth moving before the machine decides for you. We can map what should live in the cloud and move it without breaking your mail. Let's talk it through.