Knowledge Base

Outlook automatic replies are not delivered to external recipients


Automatic replies set up in Outlook or Outlook on the web (OWA) fail to reach external recipients. Despite the delivery failure, a sender does not get any Non-Delivery Report (NDR).


To troubleshoot the issue, refer to the following sections:


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Missing DKIM record for your email domain

If no DomainKeys Identified Mail (DKIM) record has been configured at your DNS service provider for the domain you use to send emails, your emails (including automatic replies) might fail DKIM authentication and, as a result, not reach intended external recipients.

Even though your users will not get any Non-Delivery Report (NDR), the message trace for failed auto replies will include the following entry:

Error:550 5.7.26 Unauthenticated email from <your email domain> is not accepted due to 550-5.7.26 domain's DMARC policy.

where <your email domain> is the domain that’s missing a DKIM record. 

To enable DKIM for your email domain and add the appropriate record at your DNS service provider’s system, follow the instructions from this section of the Microsoft article.

External auto replies disabled for remote domain(s)

If you add a new remote domain in the Exchange admin center (as shown in this Microsoft article), the delivery of automatic replies (OOF messages) to recipients in that domain is enabled by default. However, there might be a number of reasons when you might disable this setting (e.g. because an organization that uses the remote domain wants to limit automated emails received from your organization).

Consequently, when your users’ OOF messages are not delivered to a given remote domain, it’s a good idea to check if settings for that remote domain are correct. To do it, proceed as follows:

  1. Sign in to the Exchange admin center.
  2. Go to Mail flow > Remote domains in the left-hand navigation menu and click the affected remote domain on the list.
  3. In the pane that opens, click Edit reply types (Fig. 1.).

Accessing the reply types settings for a remote domain.
Fig. 1. Accessing the reply types settings for a remote domain.

  1. Make sure that the Allow only external out of office replies option is selected and that the Allow automatic replies checkbox is checked (Fig. 2.).


    The Allow external and legacy out of office replies option should be selected only if your users send auto replies using legacy Outlook versions like 2003 and older.

Options required to send auto replies to external recipients in a given remote domain.
Fig. 2. Options required to send auto replies to external recipients in a given remote domain.

  1. If your configuration is different from that shown in Fig. 2., modify the settings accordingly and click Save to apply your changes.

To learn more about remote domains from Microsoft’s documentation, refer to this article.

See also:

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