You set up a rule so invoices go straight into a folder, or so messages from one client get flagged. It worked yesterday. Today the invoices are back in your inbox, or the rule only seems to work when you're at your desk.
Outlook rules fail for a handful of predictable reasons. Here they are, most common first.
First: which Outlook are you using?
There are now three versions, and they handle rules differently:
- Classic Outlook for Windows: rules are under File > Manage Rules & Alerts.
- New Outlook for Windows (the toggle in the top corner of classic Outlook switches to it): Settings > Mail > Rules.
- Outlook on the web (outlook.office.com): also Settings > Mail > Rules.
(Microsoft's guide to rules in each version)
Reason 1: the rule only runs when your computer is on
This is the big one. Some rules run on Microsoft's mail servers, so they work around the clock on every device. Others are client-only: they only run inside classic Outlook on one computer, while it's open.
A rule becomes client-only if it does something only your computer can do. Microsoft's list includes rules that:
- play a sound or show a desktop alert,
- print the message,
- assign a category, flag it for follow-up at a set time, or mark it as read (in classic Outlook),
- permanently delete it,
- move it to a folder stored on your computer (a .pst file) rather than in your mailbox.
Classic Outlook shows (client-only) next to these rules. If you're on your phone or the computer is off, they simply don't run, which is why mail looks sorted some days and not others.
The fix: rebuild the rule so it only does things the server can do (moving to a normal mailbox folder, forwarding inside the company, deleting to Deleted Items). Creating it in Outlook on the web is a good way to guarantee it's a server rule.
Reason 2: another rule got there first
Rules run from the top of the list down. If an earlier rule moves a message and says Stop processing more rules, later rules never see it. In Outlook on the web and new Outlook, Stop processing more rules is ticked by default on new rules.
The fix: open your rules list, read it top to bottom, and use the up and down arrows to put the most specific rules first. Untick Stop processing more rules where you want a message to be handled by more than one rule.
Reason 3: the rule was made in a different version
Rules made in new Outlook or on the web using some conditions or actions (like "recipient address includes", categories or importance) don't appear in classic Outlook. Classic Outlook shows a warning that there are rules created with a different version, but they still run. If you can't find a rule you know exists, check Outlook on the web.
Going the other way, some classic client-side rules can't run in new Outlook and have to be recreated there. New Outlook also doesn't run rules for Gmail, Yahoo or iCloud accounts added to it. For a Gmail account, set up filters in Gmail itself, and if mail goes missing there, check your Gmail filters first.
Reason 4: the rule never ran on old mail
Rules only act on new mail as it arrives. To apply one to messages already in your inbox:
- Classic Outlook: File > Manage Rules & Alerts > Run Rules Now, then pick the rule and folder.
- New Outlook and Outlook on the web: in Settings > Mail > Rules, use the run button next to the rule. You run them one at a time.
Reason 5: the condition doesn't match what you think
"From" rules fail when the sender writes from more than one address (billing@ and noreply@, for example). Subject rules fail when the subject wording changes. Open one of the messages the rule missed, compare the exact sender address and subject, and loosen the condition, for example "from address contains" the company's domain.
Reason 6: you've run out of rule space
Microsoft 365 allows 256 KB of rules per mailbox, and an admin can't raise it higher. That's a lot, but people who've been adding rules for years do hit it, and Outlook shows an error when you try to save a new one. Delete rules you no longer need, or combine several "from" rules into one rule with multiple addresses.
Reason 7: the rule forwards outside the company
If your rule forwards mail to an outside address (a personal Gmail, an accountant) and it never arrives, your Microsoft 365 is probably blocking it. That's on purpose: automatic forwarding to outside addresses has been blocked by default for most businesses since 2021, because it's a favorite trick of attackers. The sender gets a bounce message. An admin can allow it for specific people, but think twice before you do.
While you're in there: check for rules you didn't make
When someone steals an email password, one of the first things they often do is create a hidden rule: forward copies of your mail to themselves, or move messages with words like "invoice" or "payment" straight to an obscure folder so you don't see replies to their fake invoices.
Look through your rules list in Outlook on the web. If you see a rule you don't remember making, especially one that forwards, deletes, or moves mail to RSS Feeds, Archive or another folder you never use, don't just delete it. Change your password, then tell whoever handles your IT, because it means someone else has had access. Our post on business email compromise covers what to do next.
When to call someone
Get help if you find a rule you didn't create, if forwarding to an outside address needs to work for a real business reason, or if a rule still won't behave after you've rebuilt it in Outlook on the web. For a team, an admin can also set up shared sorting more reliably with shared mailboxes or mail flow rules than with everyone's own Outlook rules.
Need a hand? Get in touch.
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