Email Delivery to Hotmail and Related Domains Blocked March 24, 2020 [RESOLVED]

On March 24, 2020 just after 5pm the Microsoft Hotmail public mail servers (including hotmail,,, and started blocking outbound email from the Ocean platform. Although we have not heard a formal explanation from Microsoft, it may be related to a spike in use of Ocean to notify patients of COVID-related updates, which triggered a spam filtering rule.

As a result, emails sent to addresses within these domains are not being delivered. We have opened a ticket with Hotmail support asking for this block to be lifted. It has been marked high priority and is being review by Microsoft management. We made it clear to Microsoft that this block interferes with the delivery of critical information for patients in the COVID-19 crisis.

We will continue to update this ticket with information as it becomes available.


2020-03-27 8:54am: The Microsoft Hotmail Delivery Support Team has reviewed our case and determined that they should not be blocking our email. They've notified us the blocking policy that was put in place has been removed, and that the removal process could take 24 - 48hrs to take effect for all affected inboxes.

We'll be monitoring the deliverability of email from Ocean to Hotmail inboxes closely and will update this article as we see the block start to clear up.

After the block is cleared, any patient emails that were not delivered because of the action taken by Hotmail on March 24th will need to be resent.


2020-03-27 5:57pm: Delivery to Hotmail inboxes has returned to normal.

Note: Emails sent between 5pm March 24th, and 8:30pm March 26th will need to be sent again.

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