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davidc0015
April 13, 2026
Question

Appian Cloud: Outbound Emails Get Blocked Intermittently When Our Shared Appian Mail Server IPs Get Added to Outlook Block List

  • April 13, 2026
  • 8 replies
  • 0 views

Hi Appian Community,

Any cloud customers experienced this issue?

Our clients report not receiving our outbound emails that have been custom configured already in the Sender field (i.e. not Process, Process Designer, Process Model, or Process Initiator that will create different sender names) but a custom and consistent sender name.

We have verified that the DNS in the SPF records contain all of our Appian site names.

We also enabled DKIM to contain a verified email signature.

However, whenever our shared Appian mail server IPs get added to the Outlook/Microsoft global block list, our outbound emails get blocked.

Any resolution that anybody implemented to get around this issue?

Thanks in advance.

8 replies

stefanhelzle0001
stefanhelzle0001
April 14, 2026

I suggest to open a support case to discuss this issue.

But, this makes me wonder. Isn't it the idea of a block list to block things?

However, whenever our shared Appian mail server IPs get added to the Outlook/Microsoft global block list, our outbound emails get blocked.
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davidc0015Author
April 14, 2026

Currently waiting for their response. The issue is as a cloud customer, the mail IPs are shared between multiple customers in the same region as my organization. So when another Appian cloud customer generates spam emails and gets reported to the Outlook block list, my organization gets the collateral damage

mikes0011
mikes0011
Brainy
April 14, 2026
when another Appian cloud customer generates spam emails

This is a pretty important allegation if true, and should probably be reported to Appian.

shubhama926776
shubhama926776
April 14, 2026

Raise an Appian Support ticket with the blocked IP (from your bounce/NDR) and ask them to request Microsoft delisting.

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davidc0015Author
April 14, 2026

We can actually request to delist it by ourselves. The issue is when another Appian customer generates spam emails and someone can add the shared Appian mail IPs to the block list again. causing collateral damage to my organization

shubhama926776
shubhama926776
April 15, 2026

We can request Microsoft delisting ourselves, but since Appian Cloud uses shared outbound IPs, another customer’s spam can get the same IP re-blocked and cause collateral impact.

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