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Rejected Mail

Rexx uses a proprietary mail exchanger (MX) which was built in 2024 by our Postmaster, exclusively for use on Rexx. The system allows us to distribute mail across several servers in multiple countries. It uses a number of spam prevention and blocking systems to protect our mail system and the privacy of our users. We have a zero tollerance policy regarding unsolicited eMail. (aka "Spam")

Banned Servers and Services
Rexx will ban entire Class-C IP address blocks. Meaning that all 255 addresses with the same starting 3 octets are banned. This is to prevent spammers on dynamic IP addresses from simply logging out and back in to get a new IP so they can continue to spam or attack our mail servers. Bans from Rexx mail servers are for 12 months. (Counted from the last connection attempt.) If a large number of connection attempts are made in a short time ("Brute Force" Method) the system will add the spammer to the system firewall automatically.

SORBS Black-Hole
In addition to our local ban lists, Rexx uses the Spam and Open Relay Blocking System ("SORBS") to block Spam, Phishing attacks and other Malicious mail. The list contains servers which are suspected of being infected, hacked or hijacked to send out mail. It also lists the residential dial-up, cable modem, and DSL users of other Internet services. Rexx does NOT maintain the SORBS black hole listing, and we can not remove you from their list. For more information see

Major eMail providers
We are aware that many people use free or low cost email providers. We are also aware that spammers often use these services to send out spam mail messages. The result is of course is inevitable. These services will become banned due to the spam messages. Major mail providers (such as Google/gmail, Yahoo, Outlook, Hotmail and AOL Mail) are removed from our local ban lists each day. An automated complaint message is generated and sent to the mail abuse departments for these providers when their servers are banned for the day so they can deal with their customers.

Sender Policy Framework (SPF)
From Wikipedia: The Simple Mail Transfer Protocol permits any computer to send email claiming to be from any source address. This is exploited by spammers and scammers who often use forged email addresses, making it more difficult to trace a message back to its source, and easy for spammers to hide their identity in order to avoid responsibility. It is also used in phishing techniques, where users can be duped into disclosing private information in response to an email purportedly sent by an organization such as a bank. (See for more information.)
SPF allows the owner of an Internet domain to specify which computers are authorized to send mail with envelope-from addresses in that domain. Rexx uses the SPF authentication framework to verify a server is authorized by the domain owner to send mail for those domains. This helps prevent users from impersonating other mail service providers,

Rexx user abuse reporting
Although Most Rexx subscribers have been with us for many years, we do realize it is possible for Rexx customers to send abusive or unsolicited advertisements. Several users on Rexx maintain mailing lists, which require a valid internet mail address to send a subscribe message. To report unlawful, abusive, unwanted or malicious email originiting from or, please forward a complete copy of the message (including the full message headers) to

Mail error codes
When an incomming e-Mail is Rejected by Rexx, an error code is given which identifies the reason the e-Mail or connection
is being Rejected. The error code appears at the beginning of the error message text.

Code   Error Name Description
540 Spammer Banned Spam messages(s) were recieved from within this CLASS-C block of IP addresses on one of our Unix Operating System Accounts.
541 FROM not allowed The name given in the FROM header has been used on multiple incomming spam messages, and is no longer accepted by Rexx as a valid sender.
542 Domain Name Banned   All Mail from EVERY server using this domain name have been banned due to multiple Spam messages.
543 Harvester Banned An e-Mail address harvester attacked one of our mail servers from within this block of IP addresses. (An e-Mail harvester will try hundreds or even thousands of random e-mail addresses hoping to find valid Addresses it can send Spam e-Mail to.)
550 Spammer Banned Spam message(s) were received by our users from within this CLASS-C block of IP addresses.
553 Invalid Header   This is a general mail system error, indicating some required piece of information (such as the server ID or sender username) is missing. The exact cause will be listed in the error message.
554 E-Mail Marketer A host in the IP Block is owned by an E-Mail marketing company which has attenpted to break-in to our servers, or used a dictionary (or other) attack on our servers.
555 Black Hole The IP address or server you are sending from has been black-listed on SORBS. (See above information about SORBS) (Cached)
556 Black Hole The IP address or server you are sending from has been black-listed on SORBS. (See above invormation about SORBS)
557 Protocol Ban A Host in this block has made too many connection attempts using an invalid protocol, or using invalid authentication
558 Spoofed This error occurs when you try to send a mail message to a Rexx customer saying you are Rexx Customer Service. This causes an instant PERMANANT ban.
559 Relay Denied Your mail message is addressed to someone on another server, and you are not a Rexx customer. We do not relay messages from unknown users to other mail servers.
560 Phishing A host in this IP block send a Phishing E-Mail to one or more of our users.
561 DSL/CABLE The IP Block is owned by another ISP, DSL provider, or Cable service. These users are directed to use the mail server of their provider. Rexx will not accept mail from these IP addresses, as they are not our customers.
590 AUTH Violation An attempt was made to send a mail message impersonating a Rexx user or server (See Note 1)

Note 1: Rexx is a Unix System, so most legitimate mail from Rexx users comes from within the Rexx Unix Shell environment. ANY mail, wether or not the username actually exists, incomming to our SMTP mail server saying it is from a Rexx user address will be asked for authentication. Failed authentication is assumed to be from a spammer and causes an immediate disconnect, and a one year ban for the entire Class-C IP Address block the connection came from.