Some troubles shot in the order of events in email to case conversion process.

Reference- http://dynamicscrmcoe.com/email-case-automatic-conversion-learnings-lesson-5/

1. Customer sends email to one or more of the queues.
2. Email arrives in Exchange. This can be confirmed by logging in as recipient queue credentials on webmail or office365.com.
3. Email router syncs this email into CRM. This creates records visible in Home > Service > Activities as Emails.
   1. Email sender is not identified.
      1. We had a systemuser for each queue email address. That was set as the owner of the queue record to fulfil another project specific requirement. Check personal email setting for queue owner systemuser to auto-create contact for new email senders.
   2. Emails are not coming from Exchange.
      1. Ensure that Email router is
         1. Setup
         2. Configured for environment for server side sync
         3. Active
         4. Not logging any errors in Log file (suspected queue email address is keyword)
      2. Ensure queue has an email address.
      3. Approve email for queue.
      4. Ensure emails are received in exchange mailbox using webmail or office365.com.
4. Sender field of the email has two possibilities:
   1. If the email was sent from an external user (gmail/hotmail/othercompany.com etc) for first time, a contact record should be created for the sender.
      1. Contact not created
         1. Check personal email setting for queue owner to auto-create contact for new email senders.
   2. If not, and if the sender is an internal user (systemuser), who also has a @clientcopanyname.com email address, then there are chances that because of accounting/billing needs the equivalent contact record is already created and exists in CRM. In this scenario where both record types have same email address, CRM can choose any record to mark email as sent from.
      1. Sender may be set as ‘contact’ when contact exists: it was observed that for first email from an internal sender, CRM creates a contact record as per queue owners personal email settings.
      2. Sender may be set as contact even when contact does exist: CRM may choose ‘systemuser’ and not contact.
         1. Cases are not created with case conversion rule waiting with message detail InvalidCaseException.
            • Check if subsequently you use sender as on case form. We used it for a custom lookup to ‘contact’. Process fails trying to set a systemuser record as value for a lookup to ‘contact’. Remove this reference if not needed.
            • We resolved that Client will maintain a link between systemuser and equivalent contact (systemuser.sg_equivalentcontactid) in CRM and also created and deployed a plugin on pre-create of email to replace systemuser from sender parties with equivalent contact as per the value in lookup on systemuser CRM form. Ensure this plugin step is enabled.
5. The Email arrives in the queue
6. Email to Case conversion rule converts that into a case
   1. If the case was sent to a single queue it creates only one case. But, if it was sent to multiple queues, one case will be created per queue, and then merged.
      1. Cases are not created
         1. Make sure emails are received in exchange mailbox using webmail or outlook.office365.com as per 3.2.3
         2. Ensure the case conversion rule is active
         3. Ensure the relevant queues are active
         4. Check email background processes looking for waiting process and look into details
            • The convert rule is waiting on email with detail message “You have exceeded the maximum number of {0} characters in this field”
              • It’s mostly that you are setting a case field to a value from an email property and the field size (character limits) don’t match. Increase width on case entity field to include email field max size allowed e.g. increased size to 2000
            • The convert rule is waiting on email with detail message “The case is missing customer”
              • Leave the customerid and contacted fields unchanged when configuring convert rule item’s create case step form.
7. Cases are owned by default by ‘Workflow’ user
   1. The cases are not owned by Workflow/System Admin user by default.
      1. Ensure that the relevant convert rule is owned by that user
8. An autoreply is sent to requestor from queue email address as defined in convert rule configuration form.
9. Any subsequent emails, trigger notification to case owner, and such emails like this autoreply and replies to it or any email reply to the original email will be associated with the case as activity
   1. Emails stay in Pending send status
      1. Enable relevant Mailboxes
   2. I cannot Test and Enable mailboxes. Test fails.
      1. Check Alerts on Mailbox record
      2. Enable Email Router, retry
   3. Received emails are not associated with case
      1. Ensure CRM email tracking is enable
      2. Ensure the messages’ subject line still bears the tracking code
   4. When creating email manually from a case, user cannot send email.
      1. Error message: You cannot send email as the selected user. The selected user has not allowed this or you do not have sufficient privileges to do so.
         1. Check the email ‘From’ field, login to CRM as that user, go to personal settings > Email tab and allow others to email on behalf.
      2. User does not have send-as privilege for.
         1. Ensure Allow emailing on behalf of other users at BU level for that Security Rule.
      3. Principal user (Id=012f013c-6c5d-e511-80e7-3863bb361070, type=8) is missing prvShareActivity privilege
         1. Ensure Share Permission at User level for the Security Role. (Ref:https://community.dynamics.com/crm/f/117/t/106425)
10. Email is removed from queue.
11. Case is routed if a routing rule is in place and active.

So, which steps could you add into explanation? What are your lessons that you could have added?