Acceptance of Email

This page explains our policies for accepting email sent to, or through, our email servers.
You may have reached this page after following a link in an error message.
Please read the information on this page very carefully in order to resolve the problem as quickly as possible.

[ General Acceptance Policies ] | [ Error Message Reference List ] | [ DNSRBLS ] | [ Greylisting ]
[ How to contact the Cymru 1 Postmaster ]

General Acceptance Policies

Our policies for accepting email are as follows:

1) spam (unsolicited commercial email) of any kind is expressly forbidden.

2) Your SMTP server's IP address must have an rDNS record.

3) Your rDNS record must resolve to an IP address.

4) You may not send more than 10 emails in any one SMTP session.

5) The domain name in the "from" address in your email message must have an MX record.

6) Your SMTP server must be configured to retry sending a message at least once in the event of a temporary message refusal.

7) Your SMTP server's IP must not be listed in any of the following dnsrbl blacklists:

• spamhaus.org
• sorbs.net
• spamcop.net
• [Other blacklists may be added from time to time]

General statistics: Our hosting servers receive around 100,000 emails on average per day. Of these, only around 3000 pass our level 1 spam filters, and of these around 600 are blocked by our level 2 spam, virus and phishing filters. In other words roughly 97.6% of the email sent to our servers is spam.

Why is this important to me?
If you send an email to a Cymru 1 customer whose website and email are hosted on our servers and for any reason your message, its contents or the IP address of your SMTP server does not comply with these policies then an error message may appear on your screen or you may receive a delivery failure notification message (also known as a bounce message). In most cases the nature of the error will be shown, along with a link pointing you to this page for more information.

Here is an example of a typical delivery failure notification message:

Your message did not reach some or all of the intended recipients. Subject: [subject of your message] Sent: [date and time you sent the message] The following recipient(s) cannot be reached: [email address you tried to send a message to] on [date and time] Refused. [error message]. See: http:/www.cymru1.net/terms/emailterms.php

The nature of the problem is summarised in the [error message]. A list of common errors and more information on what they mean appears in the Error Message Reference List below. Please read through them carefully. If necessary please contact your your ISP or SMTP server administrator for assistance in rectifying the issue. You should provide them with a copy of the error message and a link to this page so that they will be able to identify and help you correct the issue as quickly as possible.

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Error Message Reference List

Refused. You have no reverse DNS entry.
In non-technical terms, this error means that the email server that you are using to send email has not been set up correctly, and you will have problems sending email to almost anyone and not just to Cymru 1 customers. This is a very serious problem.

• If you are an end-user then you should contact the company that provides you with your email services and ask them to resolve the matter as quickly as possible.
• If you are an employee using your company's email system you should contact your company's IT department.
• If you are the owner or administrator of an email server, please read the technical explanation that appears below.

In technical terms, your SMTP server's public IP address has no rDNS record. There is absolutely no good reason for any legitimate SMTP server's public IP address not to have an rDNS record. Indeed, having no rDNS record is a strong indication that the computer connected to that IP is actually a compromised PC that has become part of a spam-sending botnet, and most email servers will therefore reject all email sent from such IP addresses.

You must correct this situation immediately as not only will we not accept your email but this problem will cause you to have difficulty sending email in general. Please contact your ISP or hosting/co-location/server provider for assistance if necessary. If they are unwilling or unable to help please contact the Cymru 1 Postmaster for further advice - we may be willing to whitelist your IP address under certain circumstances.

 

Refused. Your reverse DNS entry does not resolve.
In non-technical terms, this error means that the email server that you are using to send email has not been set up correctly, and you may have problems sending email to almost anyone and not just to Cymru 1 customers.

• If you are an end-user then you should contact the company that provides you with your email services and ask them to resolve the matter.
• If you are an employee using your company's email system you should contact your company's IT department.
• If you are the owner or administrator of an email server, please read the technical explanation that appears below.

In technical terms, the rDNS record for the IP address of your SMTP server does not forward-resolve to an IP address. For example, let's say your SMTP server's IP address is 1.2.3.4, and that 1.2.3.4 has an rDNS (PTR) record of my-legitimate-email-server.co.uk. This satisfies the rule which says your SMTP server's IP address must have an rDNS record. But in order for our email servers to accept email from your SMTP server, the DNS records for my-legitimate-email-server.co.uk must also include a a DNS "A" record pointing to an IP address (e.g. to 1.2.3.4).

This is necessary because most ISPs set up rDNS records for the IPs allocated to their normal dial-up and broadband customers (to allow connections to be easily identified) but at the same time mostly set things up so that such rDNS records do not forward-resolve to an IP address. In contrast, IPs allocated to hosting servers or business broadband/dial-up users or indeed any customer that specifically asks for a static IP address in order to set up a mailserver on their network are usually provided with an rDNS record that does forward-resolve to an IP address. And since most spam is sent from normal broadband/dial-up IPs being used by compromised PCs that have become part of a spam-sending botnet, our email servers therefore reject email if the IP's rDNS does not forward resolve to an IP address.

The bottom line is that there is really no good reason for an rDNS record for a legitimate SMTP server not to resolve to an IP address. If you are a system administrator or server owner and your email is being rejected because of this issue, please contact your ISP or hosting/co-location provider for assistance. It is very easily resolved. If they are unwilling or unable to help please contact the Cymru 1 Postmaster for assistance - we will normally be willing to whitelist your IP address. Keep in mind that whitelisting your address is not the ideal solution - it really is much better to simply arrange for your rDNS (PTR) to resolve to an IP address.

 

Your address has been graylisted. Try again later.
Your attempt to send email has been temporarily rejected. Please see the Graylisting section of this page for more information.

 

Refused. Your IP address is listed in the DNS RBL at [RBLNAME]
(or a message similar to this, containing a link to a blacklist website such as spamhaus.org)
Your SMTP Server's IP address is listed in a DNSRBL blacklist (whose name will be given in the error). Please see the DNSRBL section on this page for more information.

 

Refused. Relaying denied.
You are attempting to use our servers to send email without authorisation. If you are a legitimate customer with authorisation to send email via our hosting servers then your email program is not correctly configured. Please contact the Technical Support department.

Refused. Sending to remote addresses (relaying) is not allowed.
You are attempting to use our servers to send email without authorisation. If you are a legitimate customer with authorisation to send email via our hosting servers then your email program is not correctly configured. Please contact the Technical Support department.

 

Refused. The domain of your sender address has no mail exchanger (MX)
If you are an end-user then you have probably spelled the part of your email address that comes after the @ sign in your email address incorrectly when configuring it in your email program. Please double-check your email settings and contact your ISP for assistance if necessary.

Alternatively, if you are a business or a marketing company, or you are a server administrator or owner, please read the information that follows:

Your message was rejected because the domain name in the "From" address you have used when sending your email does not have correctly configured DNS records. Specifically, there are no MX records for the domain listed in the "From:" line in the message headers.

There is no good reason for an MX record to be missing from the DNS records for a domain listed as the "From:" address and we therefore consider such messages to be spam and reject them.

For example, if you send an email with a "From:" line of "promotions@marketing.my-legitimate-domain.co.uk" but there is no MX record in the DNS for marketing.my-legitimate-domain.co.uk then we will reject your messages (even though there may be an MX record in the DNS records for my-legitimate-domain.co.uk).

We reject such emails because some spammers use made-up domain names in the "From" line (usually ones that look a bit like legitimate ones or which are made-up subdomains of legitimate ones, for example using mybank-customerservices.co.uk or customerservices.mybank.co.uk instead of the real mybank.co.uk).

To resolve the problem, please add an MX record to the domain or subdomain's DNS records.

 

Timeout. Talk faster next time.
Your SMTP server is not correctly configured or uses badly written code. We will not accept your message as this is an almost certain indication of an attempt to sent spam. In the unlikely event that you are a legitimate email sender please contact the Cymru 1 Postmaster for further advice.

 

Too many recipients. Try the remaining addresses again later.
You are trying to send a single email to more than 10 recipients at once. Do not send a single copy of an email to more than 10 recipients at once as we will not accept your emails.

 

Refused. You are not following the SMTP protocol.
Your SMTP server is incorrectly configured or badly coded. Please contact the author of your SMTP server software for advice.

 

Refused. Your domain name is blacklisted.
Your domain name is listed in an internal blacklist after it violated our Email Acceptance policy or was the source of emails of an undesirable type or quantity. Please contact the Cymru 1 Postmaster for further advice.

 

Refused. Your IP address is blacklisted.
SMTP Server's IP address is listed in an internal blacklist after it violated our Email Acceptance policy or was the source of emails of an undesirable type or quantity. Please contact the Cymru 1 Postmaster for further advice.

 

Refused. Your sender address has been blacklisted.
Your email address is listed in an internal blacklist after it violated our Email Acceptance policy or was the source of emails of an undesirable type or quantity. Please contact the Cymru 1 Postmaster for further advice.

 

Refused. Mail is not being accepted at this address.
You are trying to send email to an address that has been disabled (temporarily or permanently).

 

Refused. Access is denied.
This is a general refusal. We will not accept your email.

 

Refused. Authentication failed.
You have attempted to send email but you have used to wrong username or password.

 

Refused. Unknown authentication method.
Your email program is attempting to use a method of authentication that our servers don't understand or your email program may be contain badly written code.

 

Failed to negotiate TLS connection.
Your email program has had trouble negotiating a secure connection with our servers. We do not support this method of communication. Please disable TLS in your email program. Please read your email program's help pages or manual, or contact the program's author or publisher for more information on how to do so.

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DNSRBLS (Blacklists/Blocklists)

If your SMTP server's IP address is listed in any DNSRBL (also known as an IP or Relay Blacklist/Blocklist) then you will have problems sending email in general. If your SMTP server's IP address is listed in one of DNSRBL's that we use then we will reject your email and the [Error Message] in the mail delivery failure message you will have received will indicate which blacklist your SMTP server's IP address is in.

NOTE: If you are a Cymru 1 hosting customer and you are receiving an error message mentioning dnsrbls or spamhaus when trying to send email then your email program is not correctly configured. Please contact the Technical Support department for advice. The problem can be easily rectified.

Checking to see if your internet connection's IP address or your SMTP server's IP address is in a DNSBL blacklist:

To see if an IP address is listed in any of the major blacklists, please visit: http://www.robtex.com/ and enter the IP address of your SMTP server and/or internet connection in the box at the top left hand corner of the screen

You may also wish to use one of the many tools available at www.dnsstuff.com - including the rDNS and spam blacklist checking tools.

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Graylisting (aka Greylisting)

Graylisting (also spelled Greylisting) is an important anti-spam technique that is implemented on many of our hosting servers.

If the Error Message in the delivery failure notification you receive mentions Graylisting or Greylisting, for example as follows....

Your message did not reach some or all of the intended recipients. Subject: [subject of your message] Sent: [date and time you sent the message] The following recipient(s) cannot be reached: [email address you tried to send a message to] on [date and time] 421 Your address has been graylisted. Try again later. See: http:/www.cymru1.net/terms/emailterms.php

....THEN:

A) If you are a Cymru 1 hosting customer trying to send email out to another address through our hosting servers then it means you have not correctly configured your email program. Please contact the Technical Support department for advice.

OR

B) In all other cases it means your SMTP server is not configured to retry sending an email in a sensible way if the first attempt is not successful. Please contact the administrator of your SMTP server (usually your ISP) for assistance, being sure to provide them with a copy of the error message so that they can investigate and rectify the issue as quickly as possible.

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Contacting the Cymru 1 Postmaster

If you need help or advice in resolving a problem sending email to a Cymru 1 email server and you are either an authorised representative of an ISP or you run your own mailserver then please contact the Cymru 1 Postmaster by sending an email to postmaster@cymru1.net

If you are a Cymru 1 hosting customer please contact the Technical Support department if you require help and assistance with the information on this page - you should not contact the Cymru 1 Postmaster directly yourself.

Unless you run your own mailserver we regret that we are unable to offer advice directly to customers of other ISPs - please contact your ISP for advice and ask them to arrange for an authorised representative to contact us if necessary.

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