Nexiwave experienced a rare email delivery delay issue to Microsoft 365 hosted mailboxes between 2AM EDT March 30, 2022 to approximately 1PM EDT March 31, 2022.
What happened:
- One of our customers enrolled a new system to our service. This system had previously accumulated relatively large amount of internal alert emails (with destination to a single Microsoft 365 mailbox), in deferred state.
- Our throttling threshold was too relaxed comparing to Microsoft 365 throttle threshold.
Even though these deferred emails were destined to a single Microsoft 365 mailbox, Microsoft 365 flagged our IP in 2AM March 30, 2022
and would only allow a very small amount of traffic. Nexiwave email deliveries to Microsoft 365 mailboxes were delayed (though no emails were lost).
Actions Taken:
- We took immediate action on March 30, 2022 and tuned a much more strict threshold for this customer.
- We also requested this customer to turn off routing those internal alert emails via Nexiwave.
- After several repeated attempts to Microsoft 365 business support, Microsoft agreed to release our IP from their graylist on March 31, 2022.
All delayed emails were successfully delivered after one hour of Microsoft's action.
Further Corrective Measures:
- We plan to further study on our throttling practice against major email service providers.
- We plan to add features so newly enrolled systems will automatically face much strict throttling threshold.
We thank you for your patience in this matter. We are confident that, with the measures listed above, this should not happen again.
