If this does not resolve the issue, further investigation will be required to identify why Microsoft Outlook has not synchronized with Office 365.
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.
But, then I saw when I write new emails, these newly sent emails do not appear in the Sent folder in Outlook 2011.
The same problem was observed in Outlook 2016 by my friend.
Synchronization between Exchange server and Outlook is quite smooth in most situations.
But sometimes due to bad network connection or hardware defects, synchronization can fail wholly or partially.Failure of Exchange OST Synchronization happens due to the corruption or damage of OST files too.Exchange OST Synchronization issues disturb Outlook users in different ways: After deleting/renaming the old OST file and creating a new one, you may find some data missing from the original OST file.There are three key points to note: 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 . There are a number of reasons that this can occur - such as large mailboxes or .This is when some work is left unsaved to the Exchange mailbox from the OST files.