In WHM go to
Main >> Service Configuration >> Service Manager
and enable Run another copy of exim on port 2525 amd then try to send your mails again.
Also are you trying to send mails using mail client, if so configure it to listen smtp on port 2525 instead of port 25 because some ISP's block port 25.
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The port 25 seems to be blocked in your ISP's end . Most of the server has an alternative port 26 and it is active for SMTP . Just try to change the outgoing SMTP port to 26 in your mail client , then try to send emails .