error rblsmtpd or similar

This means that the IP address from which the email is being sent is on a blacklist. Normally, this happens with dynamic IP connections, it is possible that they have assigned you an IP that has sent spam and has been banned.
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The way to solve this problem is by turning off your router for 30 minutes and turning it back on, this will change your IP and probably not be banned.
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Useful links:
How to know my IP:
​http://ip.profesionalhosting.com
How to know if my IP is on a blacklist:
​http://www.profesionalhosting.com/soporte-en-linea/como-saber-si-mi-ip-esta-en-alguna-lista-negra-preg318.html
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In case you cannot change your IP because it is fixed, a quick solution is available here:
​http://cbl.abuseat.org/lookup.cgi
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Then enter your IP in the form, look for the link at the bottom "Request delisting of .." and click on it. In 30 minutes it will work normally again. If the ban is repeated frequently, you should check your equipment as it is possible that one of them has a virus.