Your e-mail provider is blocking your outgoing e-mails because your IP address has been listed as a source for Spam in the Barracuda Black List (DNSBL). See: http://www.dnsbl.info/dnsbl-details.php?dnsbl=b.barracudacentral.org At the top is "Quick Blacklist Check:", with your IP in the box. Click the button that says "Check this IP". You will see that your IP address is on the list.

First of all, if you yourself are sending spam, then that is the main problem, and do not deserve any help.

Otherwise, work with your Internet Service Provider to find out why your IP address is in the Black List, so you and they can get it off the list.

Thank you for help. I managed to unblock my outgoing e-mail but for a period of 30 days to check if it is not sending spam. As I am not sending spam I was asking my ISP for help to check the reason for black listing but they answered that it was not possible. Are there any other possibilities to investigate this problem? Wlodek

If you are not the one who sent spam, then it was another customer of your ISP.

The IP address your Internet Service Provider assigned to you can change, especially if/when you need to reset the modem. The IP you have now was used by another customer with your ISP who sent spam e-mail.

That other customer spamming is certainly an issue that your ISP should deal with. Since your IP address can change, you may end up with another IP address that is black listed. That happens when ISP's don't do anything about their customers' spamming.

There is nothing that you can do but wait. If after the 30 days they black list your IP again, and you still have the same IP, then you or someone else with access to your Internet is being labeled a spammer. Make sure you are using wireless security so strangers can't use it.

I have order my internet access with fixed IP address and it looks that my ISP is not interested in helping me. There is a possibility that some of computers in our home network was hijacked but we have antivirus software installed, if that helps. Is it possible to hijack IP address at ISP?

I could also make this issue to a problem to my provider by changing to dynamic IP (correct?) or change to another ISP.

If you have a fixed IP address, then it is clear that your Internet connection is the one being labeled a spammer.

You could ask your ISP to change your IP, or switch to another ISP, but that is only avoiding the issue, which actual spammers will do. Don't be like them. Take ownership of the problem.

You need to question everyone who uses your Internet connection to see if they have sent out any type of e-mail that someone could have labeled as spam. An e-mail sent to many people. Especially one that advertises something.

Also, make sure that you have a wireless password setup so people can't use your Internet connection without your permission.

Then check every device that gets used on your Internet connection to make sure the antivirus is working properly and is up-to-date. Even so, working antivirus is not a 100% guarantee that a device can not be infected. Antivirus programs have to be told what to look for, and new malware may infect a device before the antivirus knows to look for it.

That is why you will also need to check every device for infections with other programs that look for bad stuff (malware).

For Windows computers (my specialty), I recommend installing and using the free versions of Malwarebytes Anti-Malware and Spybot Search & Destroy

You will need to learn how to use these properly.

If you are not good with this sort of thing, then find someone who is.

You will also need to figure out how to scan your mobile phones for malware also, but that is not something I know much about right now. There are doubtless lots of apps for that sort of thing.