Using the Signatures Tester to verify deployment

The Signatures Tester is an interactive simulator that walks a chosen From and To pair against every enabled signature and reports which rules passed, which failed, and what would have been applied. It’s the first tool you reach for on a “signature isn’t applying” ticket because it answers the question without sending real email.

The four-question triage

flowchart TD
    Q1{Did the Tester find<br/>any matching signature?} --> Q2
    Q2{Which rule failed first?<br/>Senders / Exceptions /<br/>Recipients / Date / Advanced} --> Q3
    Q3{Is the rule wrong,<br/>or is the user wrong?} --> A1
    A1{Right fix?}
    A1 --> F1[Rule wrong<br/>→ edit Senders or Exceptions]
    A1 --> F2[User data wrong<br/>→ User Details Editor or directory]
    A1 --> F3[Tester not flagging it<br/>→ open Diagnostic Logs<br/>for live mail-flow check]

Walk the four questions in order. Each one feeds the next.

1. Did the Tester find a match?

Sidebar, Signatures Tester. Pick Server-side signatures tester if the customer is on server-side, Client-side signatures tester if they’re using the Outlook Add-in. Enter the user’s email in From (one address; aliases need the Alias addresses feature enabled or you’ll get a “Domain not valid” error) and the recipient in To. Optionally fill Subject and message. Click Test.

The Results screen lists every enabled signature and shows whether it would apply.

2. Which rule failed first?

Click Details on a signature to see the rules breakdown. The Tester checks, in order:

• Enabled for client-side or server-side
• Senders (the From rule)
• Exceptions (the From-block rule)
• Recipients (internal or external; included or excluded recipients)
• Date and Time
• Advanced Rules (server-side only)

Each rule shows a green tick (passed) or yellow cross (failed). Rules that were never set are greyed out. The first failure is usually the cause.

3. Is the rule wrong, or is the user wrong?

Two different fixes:

• Rule wrong. The Senders tab targets the wrong group, the Exception list excludes the user it shouldn’t, the recipient type is “Internal Only” but the user is sending external. Edit the rule.
• User wrong. The user’s directory data missed a field the signature relies on. The Tester’s preview shows blank fields when the data is missing. Fix the directory record (or delegate via the User Details Editor).

4. What if the Tester says it should apply, but real mail still has no signature?

The Tester only evaluates Exclaimer’s own rules. It cannot evaluate:

• The “Identify Messages to Send to Exclaimer Cloud” transport rule in Exchange Online
• The Exclaimer Exchange Transport Agent
• Google Workspace Content Compliance rules

If those upstream rules block the message from reaching Exclaimer, the Tester will report success but no signature will appear. That’s when you escalate to the Diagnostic Logs (covered in the Advanced course’s troubleshooting lesson).

A worked ticket: Northwind Logistics

Northwind Logistics, mid-market warehouse operator. A driver opens a ticket: “My signature has no phone number when I email customers, but my colleague’s does.”

1. Open the Tester

   Sidebar, Signatures Tester, Server-side signatures tester. From: the driver’s email. To: a customer’s email (or any external address you control).

2. Read the rules breakdown

   Click Details on the matching signature. All rules pass. The signature is applying. So the issue isn’t a rule failure.

3. Look at the Preview

   The Designer preview pane, with the driver’s email in the search bar, renders the template against their actual directory data. The {Mobile} field is blank.

4. Check the directory

   Microsoft 365 admin centre, the user’s profile. Mobile field is empty. The colleague’s record has a mobile number; the driver’s doesn’t.

5. Decide the fix

   Either get HR to populate the directory (right answer for an MSP that owns onboarding) or enable the User Details Editor on the appropriate field so the driver can self-serve. Don’t hardcode the number into the template; that breaks for the next driver.

What this is NOT

• Not a real send. The Tester does not put a message on the wire. It evaluates rules and renders a preview. If you need to confirm DKIM, SPF, or final on-the-wire formatting, you still need a real test send.
• Not a multi-recipient simulator (server-side). Server-side testing accepts one From and one To at a time; client-side accepts up to ten recipients. For multi-recipient scenarios on server-side, run the test multiple times.