Hello Charlie. Thank you for your reply.
It is a long story, but this is it: my ISP provider loaded an anti SPAM blacklist from abuseat.net and they didn´t follow the instructions correctly. One day I began to notice that when I sent an email to somebody with the same ISP and domain, the message bounced with an error msg. indicating that I was listed as SPAMMER and my email rejected considering my IP address. Consulted the guys that administrate the blacklist, they confirmed that not any of the IP addresses that I showed in my bounced sample messages were listed and that they were having this same problem with many ISP providers all around the world that checked for neighbour IP´s and IP´ranges, filtering their own not-guilty users. So what ? OK...for the next 24 hours - they said - try to switch your modem off and back on for 5 to 10 minutes and reboot your server so you can get a new dynamic IP address from your ISP, and probably your traffic will return to normal in a couple of days. This was true and the problem seemed to be solved as days passed by, but now is here again. The list administrators sent an email to my ISP telling them that they were going to be banned from the list if they persisted in this erroneus technical behaviour. At this moment if I send an email to my own account, from my own Internet connection and it bounces.
For this second stage of the battle, I need to refresh my IP address to make some testing and for this I have to reboot the server every time. It would be better to have some way to do this by software, stopping and restarting PPoE - which I know is normally unnecessary - but it would be useful this time. Any ideas ? Thank you in advance !