Even when we have configured our email server to perfection, it can happen to have problems sending to some free accounts including the Italians: libero.it, virgilio.it, alice.it, etc ... often the problem lies in the fact that the our IP is in the backlist on UCEPROTECT , or more precisely some IPs of the class to which our IPv4 belongs have carried out spam activities. That is, we are not directly on the list of IP blocked, but due to activities beyond our control we are indirectly.
UCEPROTECT, is a network that operates with very restrictive principles (in our opinion even out of time), and works with level-based filters.
- Level 1 concerns the single IP. It is often more and more common to have a shared IP, in which case even if we behave well, someone else using the same IP may not. This is why it is very important to use a dedicated IP for the email server.
- Level 2 covers the entire IP class (approximately 65,000 addresses for class B).
- The third level is the most serious, it concerns the whole provider.
The most common case is level 2 , that is, from one or more of the 65,536 IPs to which our IPv4 belongs, has made spam activities, it can happen in these cases that by sending an email to an address or to the addresses of a manager mail, it ends up in the recipient's spam or is rejected by the mail server. You can check your dedicated IP here: http://www.uceprotect.net/en/rblcheck.php
Despite having a lot of budget today it is impossible to get an entire IP class, the last block of IPv4 was assigned by ICANN in 2011. The only solution is to ask (against payment) to UCEPROTET to add our dedicated IP to the Whitelisted ( http://www.whitelisted.org/ ) in this way we would be safe from blocking our emails due to levels 2 and 3 of the UCEPROTECT filter.
These are rare events, but sometimes cyber attacks and viruses can lead to the unconscious sending of spam or dangerous emails by multiple users of a provider, the probability that an IPv4 of the class that our dedicated IP belongs to is reported is very high, there are also services that allow you to monitor these events, such as: https://mxtoolbox.com/blacklists.aspx