Webmail stucks in sending logo.

I am facing strange issue. While trying to send mails via webmail on clicking send the sending logo gets stuck and mail takes a lot of time to be delivered. Other third party clients also cannot send mail(POP, IMAP). Checked mail queue, resource usage and everything all seems normal. Also upon mail received from the user in the same server the same mail arrives 5-6 times. Upon checking the log only 1 mail was sent. WHM v94.0.4