Diagnostic-Code: smtp; 554 5.1.8 Sender Address Blocked

Diagnostic-Code: smtp; 554 5.1.8 Sender Address Blocked

Hello, we just finish a crowdfunding campaign and we are sending our backers some personalice thank you email from our Soho email  befee@qhispikayecolodge.com (linked to a gmail account) . Unfortunate after sending over 10 of this emails we were blocked. Please help us to solve this, we are not sending any SPAM, i think the error was because we were putting over 10MB of attachment per email. We have correct this by attaching the pictures using google drive. 

Thank you