Trying to sent email from an account in server to a remote end. Getting the following bounce back message.

Could not deliver message to the following recipient(s):

Failed Recipient: khams@sddksa.com
Reason: Remote host said: 451 Temporary local problem - please try later

Mails are getting delivered successfully to another remote mail address and local mail address. The IP address is not blacklisted. There are no spam filters or blocks set in Plesk and Smarter Mail. Tried sending a mail after restarting the Smarter Mail service but the issue still persists. Could anyone let me know the exact cause of such issues.