Possible issues with duplicate email addresses in [sys_user] tableSummaryBy default, <email> field in [sys_user] table is not set to be unique. This allows the assignment of the same email address to multiple users. Such duplication of email addresses is not a valid practice and can cause unpredictable behaviour(s) in the system. Hence, it is highly recommended to use unique email address for each user when possible. Some of the possible issues that can occur from duplication of email address(es): Erratic behaviour of inbound email action(s) as Email Reader scheduled job uses first matched email address which is not guaranteed to be same every time if there are duplicate email addressesImpact on outbound notifications as multiple users will have the same email address in [cmn_notif_device] tableWhen the email address is defined as {nameID}, it can impact user logins if SSO has been configured on the instanceWhen you link your ServiceNow user account to a messaging application for Virtual Agent conversations, your messaging account is automatically linked to your ServiceNow account as long as the same email account is defined for both your messaging and ServiceNow accounts. Having duplicate email addresses can cause an issue in the Conversational Integrations for Slack, Microsoft Teams, and Workplace from Facebook if you have enabled account auto-linking, which automatically links messaging users to their ServiceNow accounts using the matching email accounts.