Currently blocked?

Hi,

I'm hoping an admin will be able to help me. I'm currently getting this error whenever I try to send an email:

Unable to connect SMTP server:smtpout.mail.zoho.com Reason:Authentication failed:554 5.1.8 Sender Address Blocked

Can anyone unlock my account? service@tagyourbeats.com.

Secondly, can you let me know why it was blocked so I don't do it in the future?

I have sent a few attachments out, but they aren't high MBs. I did try and email 98 or so people, was that what caused the problem? Because I'm emailing people who have asked for updates on services.

Thanks for your help.