Email Delay in O365

Bosco Das 80 Reputation points
2024-02-12T15:25:55.9333333+00:00

Situation:

Received an email after a delay of 101 minutes in O365 Checked on Exchange Online: it says received by xxxxxxxxxx.PROD.OUTLOOK>COM using TLS1.2 Checked for email preceding the email in question as well as an email after from the same sender and recipient - no delay, however, I did notice it mentioned received by xxxxxxxxxx.PROD.OUTLOOK>COM using TLS1.2 with AES256 Am I right in saying just because the data transit was encrypted with TLS 1.2, however, at rest the data was not encrypted with AES256, that is the reason there was a delay and Mimecast had to do its due diligence to verify before the release of the email to O365

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Accepted answer
  1. Kael Yao-MSFT 37,666 Reputation points Microsoft Vendor
    2024-02-13T02:20:13.9966667+00:00

    Hi @Bosco Das,

    To determine the cause of this delay issue, to me we may need to check the logs on Mimecast side.

    For example, if you are seeing responses like below from Exchange Online:

    4.5.3 Too many recipients (AS780090)
    4.7.500 Server busy. Please try again later from [XXX.XXX.XXX.XXX]. (S77719)
    4.7.500 Server busy. Please try again later from [XXX.XXX.XXX.XXX]. (AS77712XXX)
    4.7.500 Access denied, please try again later. For more information please go to http://go.microsoft.com/fwlink/?LinkId=526653 . (AS63)

    The cause may probably be you are sending too many messages to Exchange Online within a period.

    If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".  Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

    1 person found this answer helpful.

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