I am trying to send an email with SMTP but its not working. Why is this happening?

The sending of email with SMTP protocol (TCP port 25) has been blocked due to spammers abusing our services. Please use authenticated/secure SMTP protocol (TCP port 465,587) of your mail provider. If your mail provider does only support TCP port 25 for SMTP protocol please contact support@www.limevpn.com to be allowed to use your own/custom SMTP address.