Outlook 2016 Cached Mode connection to Exchange Online no new mail

VasilMichev I have now been able to reproduce the issue on a technical laptop. It looks like Outlook is behaving as designed but for the benefit of others here are my observations. Starting Outlook for the first time means a 12 month synchronisation of emails to cache mode by default. The first folder to sync is calendar then Inbox. I used Outlook online on the same machine as the candidate mailbox whilst the cache was backfilling sent a new message. The message appeared in Outlook online but not in Outlook. However, Outlook was still synchronising the Inbox, the users in question tend to be stackers rather than filers so whilst the mailboxes are not huge they have most of their items residing in the Inbox. Whilst backfilling the Inbox new emails are not displayed. Once the Inbox is synchronised then new email is displayed automatically at the top of the Inbox, any further emails are also now displayed in the Inbox (focus of backfill has moved on to other folders) Observing the behaviour makes sense as to what is going on, the issue is exacerbated because the branch office doesn't have the best of internet links. Our mitigation is to only sync three days worth of email on the first synchronisation, this ensures basic functionality can be confirmed with the user and we can hand back the machine. Our advice is then to leave the machine in the office overnight and we change the synchronisation period to 12 months. Thanks for your help and pointers Paul