DNSBL or spam database is a black list of domain names and ip-addresses. There are dozens of different DNSBLs on the network, each of which uses its own criteria to add and exclude an IP address or domain from its list. Most spam filters use different DNSBLs to check that incoming emails are not sent from sites whose domain names are blacklisted. DNSBL is usually the first line of defense against spam.
Getting into such lists is easy, for example, in the case of suspicion of spamming, you need to make sure that nobody uses your mail server for malicious purposes. It is highly recommended to configure reverse DNS detection for the mail server. You can check the correctness of the mail server settings through our online smtp test.
Addresses-traps. Large mail services have some mailboxes that have been abandoned by their owners for a long time. Usually they wait half a year or a year, as the user does not enter his / her account, and then they start using it to calculate spam. The usage algorithm is quite simple: when a message arrives at such an email, it is spam, and the sender of the message is a spammer. This sender is immediately blacklisted by domains or IP, the sender's reputation drops, the rest of the letters are spammed or blocked at all and do not reach other destinations. It is necessary to clean the customer base, remove known traps and all inactive addresses. We also recommend that you check the letter for spam, this can prevent spam databases from entering.
Checking for blacklists will show whether the specified URL or IP address is specified in DNSBL or SURBL systems. These systems are used by system email administrators to keep spam messages open before they reach their users. Mail services also check these sheets and make decisions about sending or blocking messages.