MC346908 – MX Record TTL Support Policy (archived)

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check before: 2022-05-02




Online, World tenant


Change type:

Admin impact



We're announcing a support policy update to the Time To Live (TTL) value for MX records pointing to Exchange Online and Exchange Online Protection.

Starting May 2nd, the maximum supported TTL value for MX records will be 6 hours (21,600 seconds) or less for MX records corresponding to domains using Office 365 for email hosting.
Exchange Online recommends setting the TTL values to 1 hour (3,600 seconds) but will support values up to 6 hours (21,600 seconds).
This will help your organization fully benefit from the high availability of Exchange Online by ensuring that email for your organization is sent to the optimal endpoint in the Exchange Online infrastructure, and it requires some actions on your part.
Note: TTLs are measured in seconds and are used to set the length of time a DNS record is cached by a DNS server or client. The greater the TTL value, the longer the record is cached. When a TTL is too long, it can lead to ‘stale’ records or stale information in the DNS server’s cache. This happens when a DNS record is changed, but the unchanged version of the record is still cached in another DNS server. If the unchanged version of the record is used, it can result in traffic being sent to the wrong destination.

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