If you are using SPAMSteward's outgoing filtering service, no email should be blocked by AOL, Yahoo or Hotmail for DNS-related reasons, as our DNS is properly configured.

However, users who choose not to use our outgoing filtering service need to be particularly careful when configuring their DNS SPF records. Specifically, when removing your email server from your MX records (one of the last steps in configuring your SPAMSteward service) it is important to remember that your SPF records should not include any servers listed in your MX records, as those servers will not be sending mail out for your domain (their job is to handle inbound mail, not outgoing mail). Instead, make sure that your SPF records list your actual outgoing email server, ensuring that it is authorized to send email for your domain.

General Information (Not using SPAMSteward's outgoing filtering) .

The most common reason for AOL, Yahoo and Hotmail to block an organization's email is based on simple DNS configuration issues. These ISPs require that DNS be configured to ensure the following:

1. The public IP address that connects to the ISP's mailserver has a DNS PTR record. This is suggested by informational RFC 1912.

2. The hostname that your outgoing email server advertises in its SMTP HELO resolves. Required by section 3.6 of RFC 2821, which is on the standards track.

3. Email is coming from a mailserver authorized by the domain’s DNS SPF records to send email for the domain listed in the sender's email address. This assumes that the domain has SPF records. Discussed in experimental RFC 4408.

4. The domain listed in the sender's email address has DNS MX or A records that resolve. Required by section 3.6 of RFC 2821, which is on the standards track.

AOL has policies and procedures in place that allow them to blacklist your mailserver if more than 1:1000 email messages from your server are reported as spam by AOL users. It is very difficult if not impossible to be removed from this blacklist. If your organization sends bulk email, it is strongly suggested that you take advantage of AOL's feedback loop and follow SPAMSteward’s recommendations.

Hotmail has a tendency to put outgoing email into the recipient's junk folder if you don't include the recipient's email address in the To: header. It is recommended that you ask your Hotmail newsletter subscribers to whitelist your sending email address.

The following three ISPs each have whitelist request methods and information for senders available at:

http://postmaster.aol.com/

http://postmaster.hotmail.com

http://help.yahoo.com/help/us/mail/defer/

AOL, Yahoo and Hotmail don't make these checks, but some recipient mailservers make the following checks which are often used to try to block spam in a very error prone manner:

1. Does the hostname in the HELO resolve to the public IP address making the connection? Not mentioned in any RFC.

2. Does the hostname advertised in the HELO appear in the DNS MX records for the domain in the sender's email address? Not mentioned in any RFC.

3. Does the IP address making the connection match the IP address of one of the mail exchangers listed in the DNS MX records for the domain in the sender's email address? Not mentioned in any RFC.

4. Does the PTR record for the public IP address making the connection resolve to a hostname that resolves to the public IP address making the connection? Not mentioned in any RFC.

Therefore, when possible, please try to configure your mail system to satisfy the above four checks to maximize delivery.