1&1 Error messages on sending and receiving emails
421 invalid sender domain '<domain.tld>' (misconfigured dns?)
The domain of the e-mail address you use is not configured correctly. An A record or MX record must be assigned to your sender domain in accordance with RFC 2181. Please contact your system administrator and/or e-mail provider for them to correct the configuration and then contact us as needed.
451 Requested action aborted: local error in processing
For administrative reasons delivery of emails to this recipient address is not permitted. Please use a different method to contact the person in question and inform them of the situation.
500 Syntax error - invalid character
The email server you use has attempted to send an email with a syntax error. Please contact your administrator who should check the configuration of the email system you are using.
554 No valid recipients
The specified recipients do not exist on our systems. Please check the spelling of the email address.
550/554 RBL rejection: http://www.spamhaus.org/query/bl?ip=<IP address>
To reduce email spam reception, we use popular RBL ("Realtime Blackhole List") lists. These lists contain dynamic IP addresses and IP addresses currently known to be spam senders. In addition to this, we manage our own RBL lists based on various criteria. Please contact your system administrator and/or email provider who should check if the IP address they use is listed on one of these lists and who should then contact us as needed.
550/554 RBL rejection: local dynamic IP address <IP address>
The e-mail server you are using is provided by a dynamically allocated IP address. As Spam is usually sent from e-mail servers with dynamically allocated IP addresses, our system, as with most e-mail service providers, rejects every e-mail sent from these servers. Please contact the administrator of your system who should then contact us.
550/554 RBL rejection: broken MTA detected, see http://schizo-bl.kundenserver.de/?ip=<IP address>
The e-mail server you use identified itself with different information. Please contact the administrator of your system who should then contact us.
550/554 RBL rejection: the local postmaster has forbidden access
For administrative reasons delivery of emails to our systems is not permitted. Please contact the administrator of your system who should then contact us.
