When a user accounts is auto created in a Hybrid setup some necessary exchange attributes are missing from the user part in the on-premises AD.
So if you experience mail routing issues from on-prem to cloud users check these flags.
| msExchRecipientDisplayType | -2147483642 |
| msExchRecipientTypeDetails | 2147483648 |
| msExchRemoteRecipientType | 4 |
| proxyaddresses | SMTP:<user>@cloudshark.nl smtp:<user>@cloudshark.mail.onmicrosoft.com |
| showInAddressBook | CN=Default Global Address List,CN=All Global Address Lists,CN=Address Lists Container,CN=cloudshark,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=cloudshark,DC=nl |
| TargetAddress | SMTP:<user>@cloudshark.mail.onmicrosoft.com |
| msExchELCMailboxFlags | 2 |
| mailnickname | best samaccountname zijn |
| msRTCSIP-PrimaryUserAddress | Primary SIP veld sip:<user>@cloudshark.nl |
Also a handy script to add Exchange move flags in case of Exchange moves, CSharp/TypeEnums.cs at master · felsokning/CSharp · GitHub