Upgrading from BBCRM 4.0 versions SP6 or lower to SP9 may require that the email server credentials be re-entered.
Verify that the correct credentials are being entered under "Email services external server settings".
Prior to CRM 4.0 SP9 Legacy Email Service passwords were not case-sensitive. Next-Gen Blackbaud Communication Services (BBCS) servers are case-sensitive. Clients who have entered the password for Email Services into BBIS or CRM with a case (uppercase/lowercase) that does not match casing of the password on the server side will receive authentication errors. If they upgrade a non-production environment for testing purposes and trigger enough authentication errors, it has the potential to lock their email service account. Since the email service account is shared in production and non-production databases, a locking of the email service account from staging can also prevent processing of email jobs in production databases.
Steps to Duplicate
View Administration > Email Services > Email Service Settings to check the Connection health.