I tried sent emails with phpmailer and I got this error:

Message could not be sent.Mailer Error: SMTP Error: data not accepted.SMTP server error: DATA END command failed Detail: Unusual sending activity detected. Please try after sometime. Learn more. Use the link mail.zoho.eu/UnblockMe to unblock SMTP code: 550 Additional SMTP info: 5.4.6

I set username and password correctly but not working. Work only with gmail. I tried with another domain but it`s down. 

Can you help me? Thank you!