Scenario
When you use server-side signatures, the signature is applied after Exchange Online processes your message.
If you have enabled the Sent Items Update feature in Exclaimer, the signatures are visible when you view emails in your Sent Items folder.
However, if you are using Classic Microsoft Outlook with Cached Exchange Mode enabled, you may notice that some Sent Items do not show the applied signature.
Reason
In Cached Exchange Mode, Outlook stores sent messages locally and syncs them with the Exchange Online mailbox afterwards. Due to this synchronization delay, Exclaimer may not find the Sent Item when it attempts to apply the server-side signature. As a result, the Sent Items update can fail.
This behavior is caused by how Classic Outlook caches and syncs mailbox data, and it is beyond Exclaimer’s control.
When Cached Exchange Mode is disabled, Sent Items are saved directly to the server mailbox, allowing Exclaimer to update them successfully. If messages still do not appear correctly in Outlook on the web, this could indicate a profile or mailbox issue rather than a signature processing problem.
Resolution
Select an option below to view the related instructions:
Option 1: Disable Cached Exchange Mode for testing
To verify whether Cached Exchange Mode is causing Sent Items to miss server-side signatures, follow these steps:
- Open the Control Panel. Select Mail (Microsoft Outlook), select Show Profiles, then select Add to add a new profile.
- Enter the new profile name and select OK.
- Follow the on-screen instructions to configure your email account in the new profile. Select Finish when the configuration is complete.
Using a fresh profile ensures there are no existing cache issues or corrupted settings affecting the test.
- Open Classic Outlook using the new profile.
- Go to the File menu, select Account Settings, then select Account Settings again.
In the Email tab, select your Exchange account from the list.
Select Change… The Exchange Account Settings window is displayed.
Uncheck the Use Cached Exchange Mode download email to an Outlook data file option. Select Next, then Finish.
Restart Outlook to apply the change.
Compose a new email. Check the Sent Items folder in the live mailbox (for example, via Outlook on the web) to confirm if the server-side signature appears.
If the signature now appears in the Sent Items, the issue was caused by Cached Exchange Mode and is resolved.
Option 2: Use Client-Side signatures (recommended if Sent Item visibility is important)
If every Sent Item in Classic Outlook must always show the signature, consider using Client-Side signatures instead of relying on server-side replacement.
With Client-Side signatures:
The signature is applied before the email is sent.
The Sent Item is saved already, containing the signature.
No post-send update or mailbox replacement is required.
There is no dependency on synchronization timing.
For more information, see the Difference in features between Client-Side and Server-Side signatures.
This method avoids the limitations caused by Cached Exchange Mode and ensures that Sent Items display signatures consistently across all clients.