ERROR CODE :554 - 5.1.8 Sender Address Blocked

ERROR CODE :554 - 5.1.8 Sender Address Blocked

Hello, 

Since yesterday, I met this issue with sending my emails (through Zoho Recruit or Zoho mail).
Am I the only one? Why my address has been blocked. I do not send a lot of emails per day.

Please could you fix this asap ?

Regards,

Olivier