Why is my account blocked? I am the admin of our domain and Zohomail account

I am the admin of my company's Zohomail account, and I suddenly received an e-mail that my account was blocked for sending e-mail. I have not sent more than a few messages today, and we are all well within our disk usage limit at my company.

If I follow the link I get an unhelpful Unblock Me message. Please fix this. E-mail is a mission critical application for our business.

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Dear User,

We regret to inform you that your email outgoing has been blocked and you will not be able to send further emails.This was done in accordance with the Zoho Mail Usage policy.

Reason for the block : Mail Box disabled. Mail Fetch has also been disabled for any active POP accounts.

However, we realize that this might have been unintentional. To unblock, please click here.

Thanks,
Zoho Mail Team

P.S.: This is an auto-generated message. Please do not reply to this email.