When someone leaves an organization, a discussion often takes place about what to do with their mailbox and other data. For Exchange Online, the choice is straightforward:
Delete mailboxes.
Keep the mailboxes and let someone else take over the Azure AD accounts (and mailboxes).
Change mailboxes to become shared mailboxes.
Preserve them as inactive mailboxes.
Usually, the choice comes down to either a shared or inactive mailbox. Of course, the mailboxes belonging to ex-employees store other personal information in places like OneDrive for Business and Teams chat. Other information, like the documents kept in SharePoint Online sites, is by definition shared and remains accessible to other users. This discussion focuses on what to do about “leaver” mailboxes.
Shared Mailboxes
Shared mailboxes have existed in Exchange for a long time and are well understood. The advantages of transforming a user mailbox to be a shared mailbox are:
The mailbox remains online and is accessible using any Outlook client. It appears in Exchange address lists like the GAL and can continue to receive inbound emails.
Users can receive permission to access and recover mailbox contents. If necessary, administrators can grant users Send As and Send on Behalf Of permissions to allow them to send emails from the shared mailbox.
When a user mailbox becomes shared, it no longer needs an Exchange Online license unless it is larger than 50 GB or has an archive.
If necessary, administrators can easily change the mailbox back to become a regular user mailbox. At this point, it must have an Exchange Online license.
Changing a mailbox to be shared is a good approach when it’s necessary for other users to take over responsibility for the work of a departed employee. For example, the manager of a sales representative who leaves the organization needs to follow up on customer engagements and commitments. Privacy can be a big concern when someone gains access to another person’s mailbox because there’s probably some personal material among business-related emails. For this reason, organizations often limit access to a mailbox for a set period after which the mailbox is deleted.
Inactive Mailboxes
In an on-premises organization, it doesn’t matter if leaver mailboxes remain online. Licenses are not required because no one uses the mailboxes. If storage is available, leaver mailboxes can stay in place for as long as the organization wishes.
The situation is different within Office 365 as Exchange Online removes unlicensed mailboxes soon after the deletion of their owner’s Azure AD accounts. To make it possible for organizations to retain leaver mailboxes for compliance purposes, Microsoft introduced inactive mailboxes several years ago. If a hold applies to a mailbox or retention labels with holds exist on items in a mailbox, Exchange Online won’t delete the mailbox following the removal of its owner’s account. Instead, Exchange Online puts the mailbox into a hidden and inactive state. The content of the mailbox remains indexed and discoverable and can be found by eDiscovery searches.
The important things to remember about inactive mailboxes are:
Inactive mailboxes remain online until the last hold (policy or retention label) lapses or an administrator removes a litigation hold on the mailbox. At this point, Exchange Online will retain the mailbox in a soft-deleted state for a further 183 days and then permanently removes the mailbox. Inactive mailboxes don’t need any type of license. Microsoft is reducing the recovery period to 30 days from September 2022 (it won’t make much difference).
Inactive mailboxes are invisible to normal client interfaces, like OWA and Outlook desktop. They do not appear in Exchange address lists and cannot receive new emails.
To access mailbox content, administrators must either recover or restore an inactive mailbox. Recovering an inactive mailbox makes it active and usable again. Restoring means that material from the inactive mailbox (or its archive) is merged into another mailbox.
Essentially, inactive mailboxes are a compliance tool. They facilitate long-term storage of mailbox content to ensure that the material in the mailboxes remains accessible if necessary. Inactive mailboxes are a good way to keep mailboxes of senior employees and other staff subject to regulatory oversight for extended periods. Figure 1 shows a tenant with shared mailboxes going back to February 2015 as viewed through the Microsoft 365 Purview portal.
Figure 1: Inactive mailboxes in the Microsoft Purview compliance portal
If you have the licenses needed to use adaptive scopes with Microsoft 365 retention policies, you can create a user scope for inactive mailboxes. If the organization has the need to keep mailboxes for an extended period (say, five years), it’s a good idea to create a retention policy with a five-year retention period and an adaptive scope targeting inactive mailboxes. That way, even if the retention period for other holds and retention labels expire, you’ll know that Exchange Online will retain the inactive mailboxes for the required period.
The Choice is Clear
GUI access to inactive mailboxes is via the Microsoft Purview compliance portal. That gives you a good clue about the essential choice between inactive and shared mailboxes. If you want to keep information because it’s needed to satisfy some regulatory or legal requirements, use inactive mailboxes. But if the organization needs information in a mailbox for immediate business reasons, transforming a leaver mailbox into a shared mailbox is a better choice.
Learn about Exchange Online and the rest of Office 365 by subscribing to the Office 365 for IT Pros eBook. Use our experience to understand what’s important and how best to protect your tenant.
{"id":null,"mode":"button","open_style":"in_modal","currency_code":"EUR","currency_symbol":"\u20ac","currency_type":"decimal","blank_flag_url":"https:\/\/office365itpros.com\/wp-content\/plugins\/tip-jar-wp\/\/assets\/images\/flags\/blank.gif","flag_sprite_url":"https:\/\/office365itpros.com\/wp-content\/plugins\/tip-jar-wp\/\/assets\/images\/flags\/flags.png","default_amount":100,"top_media_type":"featured_image","featured_image_url":"https:\/\/office365itpros.com\/wp-content\/uploads\/2022\/11\/cover-141x200.jpg","featured_embed":"","header_media":null,"file_download_attachment_data":null,"recurring_options_enabled":true,"recurring_options":{"never":{"selected":true,"after_output":"One time only"},"weekly":{"selected":false,"after_output":"Every week"},"monthly":{"selected":false,"after_output":"Every month"},"yearly":{"selected":false,"after_output":"Every year"}},"strings":{"current_user_email":"","current_user_name":"","link_text":"Virtual Tip Jar","complete_payment_button_error_text":"Check info and try again","payment_verb":"Pay","payment_request_label":"Office 365 for IT Pros","form_has_an_error":"Please check and fix the errors above","general_server_error":"Something isn't working right at the moment. Please try again.","form_title":"Office 365 for IT Pros","form_subtitle":null,"currency_search_text":"Country or Currency here","other_payment_option":"Other payment option","manage_payments_button_text":"Manage your payments","thank_you_message":"Thank you for supporting the work of Office 365 for IT Pros!","payment_confirmation_title":"Office 365 for IT Pros","receipt_title":"Your Receipt","print_receipt":"Print Receipt","email_receipt":"Email Receipt","email_receipt_sending":"Sending receipt...","email_receipt_success":"Email receipt successfully sent","email_receipt_failed":"Email receipt failed to send. Please try again.","receipt_payee":"Paid to","receipt_statement_descriptor":"This will show up on your statement as","receipt_date":"Date","receipt_transaction_id":"Transaction ID","receipt_transaction_amount":"Amount","refund_payer":"Refund from","login":"Log in to manage your payments","manage_payments":"Manage Payments","transactions_title":"Your Transactions","transaction_title":"Transaction Receipt","transaction_period":"Plan Period","arrangements_title":"Your Plans","arrangement_title":"Manage Plan","arrangement_details":"Plan Details","arrangement_id_title":"Plan ID","arrangement_payment_method_title":"Payment Method","arrangement_amount_title":"Plan Amount","arrangement_renewal_title":"Next renewal date","arrangement_action_cancel":"Cancel Plan","arrangement_action_cant_cancel":"Cancelling is currently not available.","arrangement_action_cancel_double":"Are you sure you'd like to cancel?","arrangement_cancelling":"Cancelling Plan...","arrangement_cancelled":"Plan Cancelled","arrangement_failed_to_cancel":"Failed to cancel plan","back_to_plans":"\u2190 Back to Plans","update_payment_method_verb":"Update","sca_auth_description":"Your have a pending renewal payment which requires authorization.","sca_auth_verb":"Authorize renewal payment","sca_authing_verb":"Authorizing payment","sca_authed_verb":"Payment successfully authorized!","sca_auth_failed":"Unable to authorize! Please try again.","login_button_text":"Log in","login_form_has_an_error":"Please check and fix the errors above","uppercase_search":"Search","lowercase_search":"search","uppercase_page":"Page","lowercase_page":"page","uppercase_items":"Items","lowercase_items":"items","uppercase_per":"Per","lowercase_per":"per","uppercase_of":"Of","lowercase_of":"of","back":"Back to plans","zip_code_placeholder":"Zip\/Postal Code","download_file_button_text":"Download File","input_field_instructions":{"tip_amount":{"placeholder_text":"How much would you like to tip?","initial":{"instruction_type":"normal","instruction_message":"How much would you like to tip? Choose any currency."},"empty":{"instruction_type":"error","instruction_message":"How much would you like to tip? Choose any currency."},"invalid_curency":{"instruction_type":"error","instruction_message":"Please choose a valid currency."}},"recurring":{"placeholder_text":"Recurring","initial":{"instruction_type":"normal","instruction_message":"How often would you like to give this?"},"success":{"instruction_type":"success","instruction_message":"How often would you like to give this?"},"empty":{"instruction_type":"error","instruction_message":"How often would you like to give this?"}},"name":{"placeholder_text":"Name on Credit Card","initial":{"instruction_type":"normal","instruction_message":"Enter the name on your card."},"success":{"instruction_type":"success","instruction_message":"Enter the name on your card."},"empty":{"instruction_type":"error","instruction_message":"Please enter the name on your card."}},"privacy_policy":{"terms_title":"Terms and conditions","terms_body":null,"terms_show_text":"View Terms","terms_hide_text":"Hide Terms","initial":{"instruction_type":"normal","instruction_message":"I agree to the terms."},"unchecked":{"instruction_type":"error","instruction_message":"Please agree to the terms."},"checked":{"instruction_type":"success","instruction_message":"I agree to the terms."}},"email":{"placeholder_text":"Your email address","initial":{"instruction_type":"normal","instruction_message":"Enter your email address"},"success":{"instruction_type":"success","instruction_message":"Enter your email address"},"blank":{"instruction_type":"error","instruction_message":"Enter your email address"},"not_an_email_address":{"instruction_type":"error","instruction_message":"Make sure you have entered a valid email address"}},"note_with_tip":{"placeholder_text":"Your note here...","initial":{"instruction_type":"normal","instruction_message":"Attach a note to your tip (optional)"},"empty":{"instruction_type":"normal","instruction_message":"Attach a note to your tip (optional)"},"not_empty_initial":{"instruction_type":"normal","instruction_message":"Attach a note to your tip (optional)"},"saving":{"instruction_type":"normal","instruction_message":"Saving note..."},"success":{"instruction_type":"success","instruction_message":"Note successfully saved!"},"error":{"instruction_type":"error","instruction_message":"Unable to save note note at this time. Please try again."}},"email_for_login_code":{"placeholder_text":"Your email address","initial":{"instruction_type":"normal","instruction_message":"Enter your email to log in."},"success":{"instruction_type":"success","instruction_message":"Enter your email to log in."},"blank":{"instruction_type":"error","instruction_message":"Enter your email to log in."},"empty":{"instruction_type":"error","instruction_message":"Enter your email to log in."}},"login_code":{"initial":{"instruction_type":"normal","instruction_message":"Check your email and enter the login code."},"success":{"instruction_type":"success","instruction_message":"Check your email and enter the login code."},"blank":{"instruction_type":"error","instruction_message":"Check your email and enter the login code."},"empty":{"instruction_type":"error","instruction_message":"Check your email and enter the login code."}},"stripe_all_in_one":{"initial":{"instruction_type":"normal","instruction_message":"Enter your credit card details here."},"empty":{"instruction_type":"error","instruction_message":"Enter your credit card details here."},"success":{"instruction_type":"normal","instruction_message":"Enter your credit card details here."},"invalid_number":{"instruction_type":"error","instruction_message":"The card number is not a valid credit card number."},"invalid_expiry_month":{"instruction_type":"error","instruction_message":"The card's expiration month is invalid."},"invalid_expiry_year":{"instruction_type":"error","instruction_message":"The card's expiration year is invalid."},"invalid_cvc":{"instruction_type":"error","instruction_message":"The card's security code is invalid."},"incorrect_number":{"instruction_type":"error","instruction_message":"The card number is incorrect."},"incomplete_number":{"instruction_type":"error","instruction_message":"The card number is incomplete."},"incomplete_cvc":{"instruction_type":"error","instruction_message":"The card's security code is incomplete."},"incomplete_expiry":{"instruction_type":"error","instruction_message":"The card's expiration date is incomplete."},"incomplete_zip":{"instruction_type":"error","instruction_message":"The card's zip code is incomplete."},"expired_card":{"instruction_type":"error","instruction_message":"The card has expired."},"incorrect_cvc":{"instruction_type":"error","instruction_message":"The card's security code is incorrect."},"incorrect_zip":{"instruction_type":"error","instruction_message":"The card's zip code failed validation."},"invalid_expiry_year_past":{"instruction_type":"error","instruction_message":"The card's expiration year is in the past"},"card_declined":{"instruction_type":"error","instruction_message":"The card was declined."},"missing":{"instruction_type":"error","instruction_message":"There is no card on a customer that is being charged."},"processing_error":{"instruction_type":"error","instruction_message":"An error occurred while processing the card."},"invalid_request_error":{"instruction_type":"error","instruction_message":"Unable to process this payment, please try again or use alternative method."},"invalid_sofort_country":{"instruction_type":"error","instruction_message":"The billing country is not accepted by SOFORT. Please try another country."}}}},"fetched_oembed_html":false}
2 Replies to “Comparing Shared and Inactive Mailboxes”