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Calendar invitations are being sent from my email address, but Calendly is using its own smtp server.  Since I have SPF records in my DNS, the recipient’s server is rejecting every calendar notification, since it doesn’t come from Microsoft’s servers.  There does not appear to be a way to fix this.

Hey there, @Harold81878 - sorry to hear this is happening!

With Calendar invitations, the invite is actually sent by the calendar (in your case Microsoft) and not by Calendly or Calendly servers. There might be something unexpected going on here, so I will need some more information!

Can you share a screenshot of the error you are encountering, and provide any more details that might help us dig into this? Thanks! 


@Kelsi at Calendly 


Hey @Harold81878 - thanks so much for sharing this! I can confirm this is not coming from Calendly or Calendly servers (and is coming from Microsoft/Outlook within your email), but I can also provide some information that might help! This is outside of our scope and is not an issue on the Calendly side of things but I do want to help however I can.

Firstly, in this Microsoft Community post, a Microsoft agent posted steps that might help fix this. 

Then, this is taken directly from Microsoft regarding the error you are seeing: 

"This error can happen when you are trying out a Microsoft 365 trial tenant. If you receive this error before you can purchase licenses, contact support to request an exception for the low reputation IP address until you're able to purchase licenses."

Due to the error you are seeing and the issue at hand, I will otherwise have to direct you to Microsoft Support for further assistance with troubleshooting if needed!

Please reach out to them to ask about next steps. I hope this helps!


The problem is arising because my Outlook was configured with several email accounts, one of which used IMAP.  Microsoft does not use IMAP.  I am not able to convince Calendly to use Microsoft’s SMTP server instead of the IMAP SMTP that the other account in my Outlook uses. @Kelsi at Calendly 


The problem is arising because my Outlook was configured with several email accounts, one of which used IMAP.  Microsoft does not use IMAP.  I am not able to convince Calendly to use Microsoft’s SMTP server instead of the IMAP SMTP that the other account in my Outlook uses. @Kelsi at Calendly 

Hey Harold! If you need to discuss this in more depth with our team, please log into your Calendly account and click “help” to access our support team via live chat (available 24/7). You can link to this topic to reference what’s already been discussed as well. I also highly recommend you take the suggestions in my previous comment and reach out to Microsoft support to get their insight regarding this matter.

I will continue to dig in from our end to see if there is any additional information I can offer you and update if there is! Promise!