Can I use my MailBluster Account when my AWS Account is in sandbox?

You won’t be able to send any bulk emails from MailBluster while you are in sandbox mode. Also, in Sandbox mode, those 200 emails you see are for the virtual mailbox simulator, not for sending actual emails to your leads (recipients). So in conclusion, you won’t be able to send any emails from MailBluster until and unless you move your AWS account out of Amazon SES Sandbox. However, you will still be able to explore your MailBluster Account and its features..