There are typically two parts to a domain: the top-level domain (TLD) is the extension (e.g., .com, .net) and the second-level domain (SLD) is the unique domain name (e.g., the 'ipost' in ipost.com).

The subdomain goes before the SLD and is commonly used to identify a section of the main site.

We recommend keeping the subdomain name short to keep down the length of the URL in the text version of the mailing; e.g., if the company name is example.com, you might use a subdomain name of news.example.com.

There are four options available for providing a subdomain for use in iPost mailings:

1. Name Service (NS) Delegation
   • This is the preferred method for comprehensive brand identity across all email process steps.
2. Canonical Name Aliasing (CNAME)
   • Applicable when registrars or DNS hosts do not allow "NS" records for delegation.
   • Similar benefits to NS delegation however there are limitations:
     1. Certain ESPs may reveal the iPost-managed name (target) (e.g., Gmail displaying 'target.ip03.com' instead of 'your.subdomain.com.'
     2. Unlike when setting up NS delegation, where iPost handles DKIM and SPF automatically, these TXT records must be added manually when setting up a CNAME.
     3. In addition to the above records, installing an SSL certificate requires a CAA records and an additional CNAME record be added to the same server that hosts the existing CNAME record. However, some registrars or hosts do not permit adding CAA records, which restricts SSL certificate usage since CAA records are mandatory for the certificate to be installed.
     4. CNAME delegations do not support Google Postmaster tools.
3. Client-Hosted Name Service
   • All DNS records are stored at your registrar or DNS provider.
   • Not recommended due to potential disruptions and communication challenges.
   • Subject to approval by our Technical team and hourly charges apply.
4. New Domain Registration
   • Registration of a new domain with complete control assigned to iPost.
   • Not recommended due to the potential impact on deliverability and suspicion by ISPs (e.g., may be perceived as a phishing attempt).

Name service delegation, or the creation of a CNAME, enables the following:

1. Our system automatically generates a complete set of DNS records for the appropriate domain. That set includes:
   1. A records: Address Record points a domain or subdomain to an IP address.
   2. MX records: Mail eXchanger record is a type of certified and verified resource record in the Domain Name System that specifies a mail server responsible for accepting email messages on behalf of a recipient's domain.
   3. TXT records for:
      • SPF: Sender Policy Framework record is used to indicate to mail exchanges which hosts are authorized to send mail for a domain.
      • DKIM: DomainKeys Identified Mail is a protocol that allows verification through cryptographic authentication.
      • DomainKeys: A deprecated email authentication system designed by Yahoo to verify the domain name of an email sender and the message integrity.
      • DMARC: Domain-based Message Authentication, Reporting & Conformance is an email authentication, policy, and reporting protocol. It builds on the widely deployed SPF and DKIM protocols, adding linkage to the author (“From:”) domain name, published policies for recipient handling of authentication failures, and reporting from receivers to senders, to improve and monitor protection of the domain from fraudulent email.
   4. For a delegated sub-domain only, a further sub-domain “img” for hosted assets (e.g., img.news.example.com)
2. URLs in the email content are automatically replaced with new URLs that use the sub-domain so that iPost can track views and clicks. Those new URLs redirect to the original URL after recording the action.
3. The SMTP envelope FROM: field uses a tagged address at the sub-domain, so that iPost can handle bounces (via the automatically created MX records) and match them with recipient addresses.
4. At the customers’ option, the user-visible From: field in the message may use an address at the sub-domain (we call this the IBMF, “in-bound message filter”, address) to automatically process opt-out requests, out-of-office responses, etc. (also via the MX records). This is not required. The customer may use any other working email address and handle all responses themselves.

This automation frees you from having to react if we update any of our IP addresses or if a new type of TXT record becomes standard, etc.