DominioAbsoluto Postmaster

Email policies of DominioAbsoluto.net/DominioAbsoluto.com

These are the checks that are done by the incoming mail servers of DominioAbsoluto.

Connection

The AntiSpam service of DominioAbsoluto has some blacklists, public and private, that will reject all mail from listed IPs (they will be listed because spam or malware has been sent from them). The error message will be:

554 Service unavailable; Client host [XXX.XXX.XXX.XXX] blocked using rbl.dns-servicios.com; Blocked - see http://rbl.dns-servicios.com/rbl.php?ip=XXX.XXX.XXX.XXX - IP: XXX.XXX.XXX.XXX en Lista Negra por Spam/Virus...contacte con su administrador;

The sender will have to contact with his postmaster to do the request to delete the IP from the list and check if it is still sending unsolicited mail (it will cause that the IP will be listed again). The unique responsability to prevent that a client's IP is sending mail is himself or his administrator, so we can't do anything if it has a malware program or virus that is sending spam. The responsability of delete the IP from the blacklist is of the client or of the client's postmaster.

Other times, we block some hosts that send us a lot of spam. The error would be:

554 5.7.1 host hostname[XXX.XXX.XXX.XXX]: Client host rejected: Access denied.

If you receive messages like this, contact with your administrator or ISP and he will write us to postmaster@dominioabsoluto.net to solve the problem.

Mail servers must have configured the PTR record of the their IP and it has to resolve to a valid A record. If this is not satisfied, the mail will be rejected temporary with this message:

450 Client host rejected: cannot find your hostname, [XXX.XXX.XXX.XXX];

If you receive messages like this, contact with your administrator or ISP and he/it will add the necessary PTR record.

We apply rate limits to connections made by a SMTP client. If you want send us big amounts of email, contact with us on postmaster@dominioabsoluto.net or try not to send too many emails in a too short period of time. If you don't do this, your mails can be rejected temporary with this message:

421 4.7.0 Error: too many connections from [XXX.XXX.XXX.XXX];

We apply rate limits to connections made by a SMTP client. If you want send us big amounts of email, contact with us on postmaster@dominioabsoluto.net or try not to send too many emails in a too short period of time. If you don't do this, your connections will be dropped and you'll see this message:

lost connection with XXX.XXX.XXX.XXX[XXX.XXX.XXX.XXX] while receiving the initial server greeting

For end-user IP address ranges which should not be delivering unauthenticated SMTP email to any Internet mail server we apply a greylist to ensure that the server is a real server (it should retry sometimes) and it's not a bot. The temporaly error that will be received is:

If you receive a permanent error, contact with your administrator or ISP to configure correctly the mail server.

HELO/EHLO

The HELO or EHLO command of the SMTP protocol, is used by the mail servers as a greeting of the client server that tries to send a message to our server. It has to be in the correct format as is described in RFC5321 section 4.1.1.1, with the name of the domain or the IP of the server that is trying to connect.
If is not correct, the rejection message will be:

554 <XXX.XXX.XXX.XXX> Helo command rejected: need fully-qualified hostname

If you receive messages like this, contact with your administrator or ISP and he/it will correct the parameter of this SMTP command.

MAIL FROM

Emails with FROM that doesn't have a direct DNS resolution to an A record or to a MX record, will be rejected (RFC 2505). The FROM addresses need to be in a FQDN ("Full Qualified Domain Name") format, user@domain.com, like the RFC of SMTP says.
The rejection message generated by this cause will be:

450 <user@nodomain>: Sender address rejected: Domain not found;

Domains that have a CNAME record or IP like as the resolution of the MX records will be rejected too. This is not permitted like RFC 2181 section 10.3 says.

If you receive messages like this, contact with your administrator or ISP and he/it will correct the DNS configuration of your domain.

We've internal blacklists that will filter messages from domains that do, for example, massive mailings or malware sents. Is not a good policy to reject messages by domain but sometime, we can do it if we receive a lot of mails from an especific domain. The error message will be:

450 <user@domain.com>: Sender address rejected: Access denied;

If you receive messages like this, contact with your administrator or ISP and he/it will contact with us at postmaster@dominioabsoluto.net.

In a near future, SPF checks will be done to every mail. If the check fails, mail will be rejected. Now, this checks are done in the content filter, so if the SPF check fails, possibly, the mail will be tagged as spam or it will be deleted.

RCPT TO

Messages with a destination of a domain that is not of our responsability will be rejected, our servers are not open relays. You will see a message like this if you try to send a message to an external domain through our servers:

554 5.7.1 <user@domain.com>: Relay access denied;

If you receive messages like this, contact with your administrator or ISP to check your mail configuration.

We've blacklisted some recipients too; viruses and worms use to send messages to tipical addresses so some of them are rejected by default. You will see this message:

554 5.7.1 <user@domain.com> Recipient address rejected: Access denied;

If you receive messages like this, contact with your administrator or ISP and he/it will contact with us at postmaster@dominioabsoluto.net.

Messages to an inexistant destination will receive next message:

550 5.1.1 unknown@domain.com: Recipient address rejected: User unknown in relay recipient table

If you receive messages like this, verify the email you are trying to send message really exists, or contact with your administrator or ISP and he/it will contact with us at postmaster@dominioabsoluto.net.