Email sending stopped working on Siteground Cloud server

Hi! The plugin is super cool and it was working perfectly when my website is hosted with Wp-Engine server. Now I moved my website to Siteground Cloud server and it stopped working. However, when I deactivated the plugin then again the email starts working but then it is delivering in spam/junk folder.

My DKIM and all TXT records are showing as verified on my Amazon AWS Console

Verification Status: verified
DKIM Status: verified
Enabled for Sending: Yes

This is the error message keep getting when I send test email from plugin’s page:

Error executing "SendRawEmail" on "https://email.us-east-1.amazonaws.com"; AWS HTTP error: Client error: <code>POST https://email.us-east-1.amazonaws.com</code> resulted in a <code>400 Bad Request</code> response: <ErrorResponse xmlns="https://ses.amazonaws.com/doc/2010-12-01/"> <Error> <Type>Sender</Type> <Code>MessageReje (truncated...) MessageRejected (client): Sending paused for this account. For more information, please check the inbox of the email address associated with your AWS account. - <ErrorResponse xmlns="https://ses.amazonaws.com/doc/2010-12-01/"> <Error> <Type>Sender</Type> <Code>MessageRejected</Code> <Message>Sending paused for this account. For more information, please check the inbox of the email address associated with your AWS account.</Message> </Error> <RequestId>207abefe-4ed7-4013-9c11-4aa1f47c0f04</RequestId> </ErrorResponse>

Please suggest what causing issue as this was working on previous server but stopped when we moved to new server.

Thnaks.