Outgoing E-mail Blocked

Outgoing E-mail Blocked

Hi. The last few days I've been unable to send e-mails through my e-mail client, Thunderbird. When using Zoho Mail I can send e-mails, but in Thunderbird I receive an error message and nothing goes through.

The message reads as follows:

"An error occurred while sending mail. The mail server responded: 5.1.8 Email Outgoing Blocked. <a href=https://www.zoho.com/mail/help/usage-policy.html target=_blank>Learn more.</a>. Please check the message and try again.".

I've also attached a screenshot of the message.

I would really appreciate some help with this.

Thanks