Hi @Elakiya ravi 

Thank you for posting your question in the community!

Free accounts are limited to 250 contacts or up to 500 email sends per month. You can find this in the account settings under billing. For example:

Its possible you’ve hit this monthly allocation with the first few sends you already sent. 

That said, if you had some of your 500 emails available, you would be able to send emails via campaigns or flows until you received the 500 cap on the free account.

I hope this helps!

@In the Inbox