Remote Server returned '550 5.7.705 Access denied, tenant has exceeded threshold.

[claireturner]

what does this mean? Why can't I send emails?

[#2]

Hi @claireturner 

Remove blocked users from the Restricted users portal - Office 365 | Microsoft Learn

Please refer to this documentation

[#3]

@claireturner 

Base on the error message, it seems Exchange Online Protection (EOP) filters identify a very large volume of suspicious email coming from your tenant and triggers a block of outgoing email action
Several different reasons may occur, please make sure your Exchange in terms of SPAM and report to Microsoft to unlock

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