Mail Outgoing blocked. Unknown

Mail Outgoing blocked. Unknown

Help. Last night I sent several or around 10 emails to Craigslist potential customers requesting my services and now I've been stopped by Zoho SMTP

Your Outgoing has been blocked and you will be unable to send emails.  Click here  to get unblocked.
Block Type: Mail Outgoing blocked. Unknown

So is it unknown because Craigslist flagged me?

Should I never use Zoho mail to contact craigslist ever again?

My business is shut down if you disable the SMTP and I need a fix ASAP.

emailed support
support@zohomail.com  
support@zoho.com
for my account at mark@seogame.com from seogame@gmail.com