You have enabled the Sent Items Update feature in Exclaimer Cloud - Signatures for Office 365, so signatures are visible when a sender views email messages in their Sent Items folder.
When the Cached Exchange Mode option is enabled in Microsoft Outlook, no signature is visible for sent messages. However, if the same messages are viewed with Outlook Web Access (OWA) - or if Cached Exchange Mode is disabled, the signature is visible.
There are three key points to note:
- Microsoft Outlook displays sent items from an Outlook Data file (.OST) on each user's local computer
- .OST files are synchronized with Office 365 mailboxes
- The Sent Items Update feature updates sent items from Office 365 mailboxes
When the Cached Exchange Mode option is enabled in Microsoft Outlook, there can be times where sent messages displayed in Microsoft Outlook are not the most recent. This is where the Office 365 mailbox is not synchronized with the .OST file (or vice versa). There are a number of reasons that this can occur - such as large mailboxes or .OST files, or if particular add-ins are installed in Microsoft Outlook.
Initially, you can confirm if the Sent Items Update has updated the sent item, or if Microsoft Outlook is displaying old data, by logging into the user’s mailbox using Outlook Web Access.
Having confirmed that the cause lies with synchronization (i.e. that old data is being displayed in Microsoft Outlook), we advise reducing the size of the user's Sent Items folder and/or disabling Microsoft Outlook add-ins.
If this does not resolve the issue, further investigation will be required to identify why Microsoft Outlook has not synchronized with Office 365.