You are surely aware of the commercial harm done by spam-mails. Therefore we are forced to secure our systems and prevent spam wherever possible. To block as much spam as we can, we are using different techniques like blacklists, greylisting, spf etc.

You are viewing this page most likely because one of your e-mails to us was blocked. If so, please contact us by other means, so we can sort out the problems.

Your e-mail was probably blocked since your e-mail system does not comply to international e-mail standards. These are the tests we are enforcing:

• We only accept mails for valid e-mail addresses. The error 5.7.1 recipient <whatever@seceidos.de> unknown means that we do not recognize this e-mail address.
• We check if your IP address is listed in the blacklist at zen.spamhaus.org. We have no influence on the contents of this blacklist. The blacklist contains addresses of known spammers, open-relays, compromised systems etc. Moreover it contains dynamic IP addresses if the corresponding ISP denies direct mail transfer from those addresses. You can check yourself on the pages of zen.spamhaus.org if and why your IP address is listed and can apply for delisting. WARNING: If your IP address is listed, it can and probably will mean that one of your PCs is virus infected and is sending spam. We urge you to take an intensive look at your network security before applying for delisting.
• On some of our systems we will not accept mail from dynamic IP addresses. Most of the spam is sent from those systems due to virus infections etc. In this case please either send your mail through your companies mail server (via VPN, SMTP AUTH or other means) or use the smarthost of your Internet Service Provider.
• We will only accept Delivery Service Notifications (DSN) and similar mails if they contain references to our own e-mails. Since many spammers use faked addresses we could otherwise be swamped by thousands of DSNs for e-mails, we never sent. Since all e-mail systems we tested add suitable references to our mails in DSNs and similar mails, this should not be a problem.
• Your mailer may not claim to be part of Seceidos in the HELO statement.
• As stated in RFC2821 your mailer must supply its full qualified domain name in HELO. We will accept your IP address instead if it corresponds to the IP address you are actually using.
• E-Mails from the so called Null-Sender <> will only be accepted if directed at a single recipient. Since these mails are used for DSNs etc. this again should not be a problem.
• We only accept mails from domains whose top level domain is registered with IANA.
• Your sender domain must be able to accept e-mails itself. We therefore test for the existence of MX records for your domain. MX records tell other systems the IP addresses of your e-mail system.
• We check the mandatory e-mail syntax as defined in RFC2821.
• We do not support pipelining. Therefore your mailer is required to wait for answers of our system before continuing with the next command.
• If you publish SPF records we will honor them. This means we will not accept mails from IP addresses you have not authorized.