All versions of HelpMaster
After upgrading Microsoft Office from Office 2010 (or earlier) to Office 2013 (or Office 365), the HelpMaster Desktop &/or Email Manager may no longer successfully send emails when utilising Exchange "Send As" or "Send on Behalf Of" rights to send from a shared or central mailbox e.g. email@example.com.
This may occur because there is a bug with Outlook 2013 and Exchange 2013 in that 'Send As' and 'Send on Behalf Of' permissions are not honoured if 'Cached Mode' is enabled in your Outlook profile. This is especially prevalent when upgrading from Outlook 2010 to 2013 because 2010 uses *.pst local cache files while 2013 now always uses *.ost cache files. It seems that Microsoft did not fully implement backward compatibility in Outlook 2013 for the use of the legacy *.pst cache files. If using Exchange Server 2013, this issue may still manifest itself even if using the new *.ost caching files in Outlook because there is both a problem in Outlook as well as Exchange 2013.
The HelpMaster email accounts are described in the HelpMaster help file. You can view this information by opening your local HelpMaster help, or on-line here http://www.helpmasterpro.com/helpfile/hh_goto.htm#desktop/html files/Email overview.htm
Emails may fail to send when sending 'As' or 'On Behalf Of' a shared or central mailbox e.g. firstname.lastname@example.org, after upgrading to Office 2013 or Office 365. Symptoms may vary depending on the version of Exchange Server being used. Sending with your own personal mailbox account should still work fine.
Office 2013 (or 365) with Exchange 2010 (or earlier versions);
In this combination one of the following steps should resolve the problem,
1. (Quick Fix) Modify your Outlook profile and deselect the "Use Cached Exchange Mode" option from your settings for each mailbox. This should resolve the issue once it is using 'Online Mode' only. If the option to disable cached mode is not available this is because your domain Group Policy has been set to lock this setting using the Microsoft Outlook 2013 administrative template (adm(x) template) in the default domain Group Policy "User Configuration" > "Policies" > "Administrative Templates" > "Microsoft Outlook 2013" > "Account Settings" > "Exchange" > "Cached Exchange Mode" > "Use Cached Exchange Mode for new and existing Outlook profiles". The "Not Configured" setting will allow turning the cached exchange mode on or off by the end user. "Disabled" will prevent cached exchange mode from being selected by all domain users, but only for NEW profile configurations. Existing Outlook profiles will still be set to use cached exchange mode and will need to be disabled manually from each user's Outlook profile.
2. (Permanent Fix) Delete your existing Outlook profile and create a new one using cached exchange mode as then Outlook 2013 will create new cache files in the new default *.ost format which should work fine with Exchange Server versions 2010 or earlier. If this does not resolve the issue then please see the linked Knowledge Base article entitled ""Send As" or "Send on Behalf Of" a shared mailbox no longer works after upgrading from HelpMaster v14 (or earlier) to v15".
Office 2013 (365) with Exchange 2013;
The above resolutions will only work if Exchange Server 2013 is updated to at least Cumulative Update 3 (CU3) which resolves the server side issue. Prior to CU2 turning ON cached mode (yes the opposite action) was the 'quick fix' if using Exchange Server 2013. Later Exchange 2013 Cumulative Updates (4-10) may also change the behaviour, the 'quick fix', and results.
NOTE: In Exchange Server 2013 granting FULL mailbox rights does not also grant "Send As" or "Send on Behalf Of" rights to the delegated mailbox. FULL rights will allow the delegate to view the shared mailbox in their own Outlook profile but not grant the necessary "Send As" or "Send on Behalf Of" rights.
If you are running HelpMaster v15.6.5 to v15.6.30 then please also see the linked article "Send As" or "Send on Behalf Of" a shared mailbox no longer works after upgrading from HelpMaster v14 (or earlier) to v15
External articles to check
Exchange 2010/2007 Send on Behalf , Send as: http://www.techieshelp.com/exchange-20102007-send-on-behalf-send-as/
How to troubleshoot e-mail messages that are stuck in your Outbox : http://support.microsoft.com/kb/262052
Why an email gets stuck in Outlook Outbox and how to delete a hanging message or make it send: https://www.ablebits.com/office-addins-blog/2013/11/12/email-message-stuck-outlook-outbox/
Office IT Pro Blog: The mysterious Outlook Outbox