Turn on smtp authentication in your mail client

client smtp email submissions (also known as authenticated smtp submissions) are used in the following scenarios in office 365 and microsoft 365:

• pop3 and imap4 clients. these protocols only allow clients to receive email messages, so they must use authenticated smtp to send email messages.
• applications, report servers, and multifunction devices that generate and send email messages .

smtp authentication protocol is used for client smtp email sending, usually on tcp port 587. smtp authentication supports modern authentication (modern authentication).

Virtually all modern email clients that connect to exchange mailboxes online in office 365 or microsoft 365 (for example, outlook, outlook on the web, ios mail, outlook for ios and android, etc. ) do not use smtp authentication to send email messages.

Therefore, we strongly recommend that you disable smtp authentication in your online exchange organization and enable it only for accounts (ie mailboxes) that still require it. there are two settings that can help you do this:

• an organization-wide setting to disable (or enable) smtp authentication.
• a per-mailbox setting that overrides the tenant-wide setting.

Note that this setting only applies to mailboxes hosted on Exchange Online (Office 365 or Microsoft 365).

disable smtp authentication in your organization

You can only disable (or enable) smtp authentication globally for your organization using exchange online powershell.

To disable smtp authentication globally for your organization, run the following command:

note: to enable smtp authentication if it is already disabled, use the value $false.

how do you know this procedure worked?

To verify that you have globally disabled smtp authentication in your organization, run the following command and verify that the value of the smtpclientauthenticationdisabled property is true:

enable smtp authentication for specific mailboxes

per mailbox settings to enable (or disable) smtp authentication is available in the microsoft 365 admin center or exchange powershell online.

use the microsoft 365 admin center to enable or disable smtp authentication on specific mailboxes

1. open the microsoft 365 admin center and go to users > active users.

   select the user, and on the flyout that appears, click mail.

   In the email applications section, click manage email applications.

   verify the authenticated smtp setting: unchecked = disabled, checked = enabled.

   when you’re done, click save changes.

   use exchange online powershell to enable or disable smtp authentication on specific mailboxes

   use the following syntax:

   The $null value indicates that mailbox settings are controlled by the organization’s global settings. uses the values ​​$true (disabled) or $false (enabled) to override the organization setting. mailbox settings take precedence over organization settings.

   This example enables smtp authentication for the mailbox sean@contoso.com.

   This example disables smtp authentication for the mailbox chris@contoso.com.

   use exchange online powershell to enable or disable smtp authentication on multiple mailboxes

   use a text file to identify mailboxes. values ​​that don’t contain spaces (for example, alias, email address, or account name) work best. the text file should contain a mailbox on each line like this:

   akol@contoso.com tjohnston@contoso.com kakers@contoso.com

   The syntax uses the following two commands (one to identify mailboxes and the other to enable smtp authentication for those mailboxes):

   This example enables smtp authentication for the mailboxes specified in the file c:my documentsallow smtp.txt authentication.

   how do you know this worked?

   To verify that you have enabled or disabled smtp authentication for a specific mailbox, do any of the following:

   • Individual mailboxes in the Microsoft 365 admin center – Go to Users > active users > select user > click mail > click manage email applications and check the value for authenticated smtp (checked = on, unchecked = off).

     individual mailboxes in exchange online powershell: replace <mailboxidentity> with the name; alias; mailbox email address or account name; run the following command; and check the value of the smtpclientauthenticationdisabled property (false = enabled, true = disabled, blank = use organization settings).

     all mailboxes where smtp authentication is disabled – Run the following command:

     all mailboxes where smtp authentication is enabled – Run the following command:

     all mailboxes where smtp authentication is controlled by organization settings – Run the following command:

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