FAQ & Support - Server Response 530: 5.7.1 Authentication required - Receive Error
Server Response 530: 5.7.1 Authentication required - Receive Error
The error message 530: 5.7.1 Authentication required can have several causes. One of the most common causes of this error message is that the outgoing mail server is listed on a DNS Blackhole List (DNSBL).
DNSBL lists are also known as spam blacklist servers. The message was consequently rejected by our system.
You can check for yourself whether an IP or a mail server is on a DNSBL list, for example via a blacklist check. To check the IP address or domain, we recommend this tool, for example: https://mxtoolbox.com/blacklists.aspx
Enter the domain or IP address of the outgoing mail server. If the result is negative, contact the sender or the administrator of the outgoing mail system.