ClickUp × Outlook: If Email Auth Fails, Try Reconnecting

Conclusion

If you're using ClickUp with the Outlook integration and notice that email authentication (SPF / DKIM / DMARC) is not passing—or not even being evaluated—try disconnecting and reconnecting your Outlook integration. It may resolve the issue.

The Issue I Encountered

In my case, I send emails via ClickUp in several workflows. Recently, I discovered that domain authentication was not being applied correctly.

A bit late to notice, but…

Initially, I assumed this was expected behavior since emails were being sent through ClickUp.

However, that wasn’t actually the case.

Before re-authentication, the state was as follows:

• SPF: not evaluated
• DKIM: not signed (none)
• DMARC: not evaluated

In other words, it wasn’t that authentication was failing—it wasn’t being processed at all.

What Changed After Re-authentication

After disconnecting and reconnecting Outlook, the situation improved:

• SPF: pass
• DKIM: pass
• DMARC: pass

This indicates that emails started being sent properly via Outlook (Microsoft 365).

Why Re-authentication Helps

I don’t remember exactly, but I vaguely recall ClickUp announcing something like:

• Outlook integration updates
• Request to reconnect accounts

It may have been related to an update in Outlook calendar integration, but I’m not entirely sure.

If you didn’t re-authenticate at that time, it’s possible that your connection was left in a partially broken state, which prevented proper authentication processing.

It’s likely that this update changed how emails are sent—shifting from ClickUp sending emails directly to routing them through Outlook (Exchange) instead.

Relationship with External Services

Even now, emails sent from ClickUp likely still go through external services.

For example, email headers include values like x-nylas-send-v3, which suggests that Nylas is likely being used internally.

Based on this, the current architecture probably looks like this:

• ClickUp (and possibly Nylas) → sends an API request to initiate email
• Outlook (Microsoft 365) → performs the actual email delivery

As a result:

• DKIM signatures are added by Outlook
• SPF aligns with Microsoft’s sending servers
• DMARC is evaluated and passes correctly

What is Nylas?

Nylas is a company/service that provides APIs to integrate email, calendar, and contacts (from services like Microsoft and Google) into applications.

Nylas One Email, Calendar and Meeting API 2026 | Nylas

I should've followed the official announcement (^^;)

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