Emails sometimes delivered to A record

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Level 1

4 points

Emails sometimes delivered to A record

My client is using an email account @mac.com. His business email mail.com.au is hosted with Microsoft 365. When he sent emails from his mac.com email to a user at mail.com.au, some emails were delivered successfully to MX record of the domain, which is pointed to Microsoft 365, while some emails were delivered to the A record of the domain, which were rejected and bounced with an undelivered message. Below are the hosts which tried to send emails to A record instead of MX record in the last 7 days.

17.58.23.***

[Edited by Moderator]

MacBook Pro 13″, macOS 12.7

Posted on Nov 10, 2024 8:24 PM

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Answer 1

KenLiuAU Author

Level 1

4 points

Nov 11, 2024 4:06 PM in response to AlWeir

This has nothing to do with Microsoft 365. Accordingly to RFC5321, SMTP client performs DNS lookup, locates MX record and sends the email to MX host. Only when MX record doesn't exist SMTP client will try to send the email to the host of A record. So basically the behavior of those Apple relay servers was wrong and incompliant to RFC5321. No matter if the MX record was pointed to Microsoft 365 or something else, this would still happen.

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Answer 2

AlWeir

Level 4

3,242 points

Nov 11, 2024 7:23 AM in response to KenLiuAU

That seems to be a Microsoft 365 question and not a Apple question

Microsoft 365 | Microsoft Community Hub

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