Several techniques, configurations, and tools that you can use to improve your deliverability rate are listed below.
Adobe Campaign checks whether a reverse DNS is given for an IP address and that this correctly points back to the IP.
An important point in the network configuration is making sure a correct reverse DNS is defined for each of the IP addresses for outgoing messages. This means that for a given IP address, there is a reverse DNS record (PTR record) with a matching DNS (A record) looping back to the initial IP address.
The domain choice for a reverse DNS has an impact when dealing with certain ISPs. AOL, in particular, only accepts feedback loops with an address in the same domain as the reverse DNS (see Feedback loop).
A tool is available to verify the configuration of a domain: https://mxtoolbox.com/SuperTool.aspx.
MX rules (Mail eXchanger) are the rules that manage communication between a sending server and a receiving server.
More precisely, they are used to control the speed at which the Campaign MTA (Message Transfer Agent) sends emails to each individual email domain or ISP (e.g. hotmail.com, comcast.net). These rules are typically based on limits published by the ISPs (e.g. do not include more than 20 messages per each SMTP connection).
For more on MX management, refer to this section.
TLS (Transport Layer Security) is an encryption protocol that can be used to secure the connection between two email servers and protect the content of an email from being read by anyone other than the intended recipients.
SPF (Sender Policy Framework) is an email authentication standard that allows the owner of a domain to specify which email servers are allowed to send email on behalf of that domain. This standard uses the domain in the email’s “Return-Path” header (also referred to as the “Envelope From” address).
A tool is available to verify an SPF record: https://www.kitterman.com/spf/validate.html
The SPF is a technique that, to a certain extent,enables you to make sure that the domain name used in an email is not forged. When a message is a received from a domain, the DNS server of the domain is queried. The response is a short record (the SPF record) that details which servers are authorized to send emails from this domain. If we assume that only the owner of the domain has the means to change this record, we can consider that this technique does not allow the sender address to be forged, at least not the part from the right of the “@”.
In the final RFC 4408 specification, two elements of the message are used to determine the domain considered as the sender: The domain specified by the SMTP “HELO” (or “EHLO”) command and the domain specified by the address of the “Return-Path” (or “MAIL FROM”) header, which is also the bounce address. Different considerations make it possible to take into account one of these values only; we recommend making sure that both sources specify the same domain.
Checking the SPF provides an evaluation of the validity of the sender’s domain:
It is worth noting that records made at the level of the DNS servers can take up to 48 hours to be taken into account. This delay depends on how often the DNS caches of the receiving servers are refreshed.
For hosted or hybrid installations, if you have upgraded to the Enhanced MTA, DKIM email authentication signing is done by the Enhanced MTA for all messages with all domains.
DKIM (DomainKeys Identified Mail) authentication is a successor to SPF and uses public-key cryptography that allows the receiving email server to verify that a message was in fact sent by the person or entity it claims it was sent by, and whether or not the message content was altered in between the time it was originally sent (and DKIM “signed”) and the time it was received. This standard typically uses the domain in the “From” or “Sender” header. To insure the security level of the DKIM, 1024b is the Best Practices recommended encryption size. Lower DKIM keys will not be considered as valid by the majority of access providers.
DKIM comes from a combination of the DomainKeys, Yahoo! and Cisco Identified Internet Mail authentication principles and is used to check the authenticity of the sender domain and guarantee the integrity of the message.
DKIM replaced DomainKeys authentication.
Using DKIM requires some prerequisites:
DMARC (Domain-based Message Authentication, Reporting and Conformance) is the most recent form of email authentication, and it relies on both SPF and DKIM authentication to determine whether an email passes or fails. DMARC is unique and powerful in two very important ways:
DMARC can leverage the reports generated by 250ok.
A feedback loop works by declaring at the ISP level a given email address for a range of IP addresses used for sending messages. The ISP will send to this mailbox, in a similar way as what is done for bounce messages, those messages that are reported by recipients as spam. The platform should be configured to block future deliveries to users who have complained. It is important to no longer contact them even if they did not use the proper opt-out link. It is on the basis of these complaints that an ISP will add an IP address to its denylist. Depending on the ISP, a complaint rate of around 1% will result in blocking an IP address.
A standard is currently being drawn up to define the format of feedback loop messages: the Abuse Feedback Reporting Format (ARF).
Implementing a feedback loop for an instance requires:
Implementing a simple feedback loop in Adobe Campaign uses the bounce message functionality. The feedback loop mailbox is used as a bounce mailbox and a rule is defined to detect these messages. The email addresses of the recipients who reported the message as spam will be added to the quarantine list.
The mechanism is immediately operational to process complaint notifications. To make sure this rule is working correctly, you can temporarily deactivate the accounts so that they do not collect these messages, then check the contents of the feedback loop mailbox manually. On the server, execute the following commands:
nlserver stop inMail@instance, nlserver inMail -instance:instance -verbose.
If you are forced to use one single feedback loop address for multiple instances, you must:
Replicate the messages received on as many mailboxes as there are instances,
Have each mailbox picked up by one single instance,
Configure the instances so that they only process the messages that concern them: the instance information is included in the Message-ID header of messages sent by Adobe Campaign and is therefore located also in the feedback loop messages. Simply specify the checkInstanceName parameter in the instance configuration file (by default, the instance is not verified and this may lead certain address to be quarantined incorrectly):
<serverConf> <inMail checkInstanceName="true"/> </serverConf>
Adobe Campaign’s Deliverability service manages your subscription to feedback loop services for the following ISPs: AOL, BlueTie, Comcast, Cox, EarthLink, FastMail, Gmail, Hotmail, HostedEmail, Libero, Mail.ru, MailTrust, OpenSRS, QQ, RoadRunner, Synacor, Telenor, Terra, UnitedOnline, USA, XS4ALL, Yahoo, Yandex, Zoho.
Adding an SMTP header called List-Unsubscribe is mandatory to ensure optimal deliverability management.
This header can be used as an alternative to the “Report as SPAM” icon. It will display as an unsubscription link in the email interface.
Using this functionality helps to protect your reputation and feedback will be executed as an unsubscription.
This functionality is available from Build 6831.
To use List-Unsubscribe, you must enter a command line similar to as follows:
List-Unsubscribe: mailto: email@example.com?subject=unsubscribe?body=unsubscribe
The example above is based on the recipient table. If database implementation is done from another table, make sure to reword the command line with the correct information.
The following command line can be used to create a dynamic List-Unsubscribe:
List-Unsubscribe: mailto: %=errorAddress%?subject=unsubscribe%=message.mimeMessageId%
Gmail, Outlook.com and Microsoft Outlook support this method and an unsubscribe button is available directly in their interface. This technique lowers complaint rates.
You can implement the List-Unsubscribe by:
The command line must be added in the additional section of the email’s SMTP header.
This addition can be done in each email, or in existing delivery templates. You can also create a new delivery template that includes this functionality.
The rule must contain the script that generates the command line and it must be included in the email header.
We recommend creating a typology rule: the List-Unsubscribe functionality will be automatically added in each email.
Clicking the unsubscribe link opens the user’s default email client. This typology rule must be added in a typology used for creating email.
Clicking the unsubscribe link redirects the user to your unsubscription form.
SMTP (Simple mail transfer protocol) is an Internet standard for email transmission.
The SMTP errors that aren’t checked by a rule are listed in the Administration > Campaign Management > Non deliverables Management > Delivery log qualification folder. These error messages are by default interpreted as unreachable soft errors. The most common errors must be identified and a corresponding rule added in Administration > Campaign Management > Non deliverables Management > Mail rule sets if you wish to correctly qualify the feedback from the SMTP servers. Without this, the platform will perform unnecessary retries (case of unknown users) or wrongly place certain recipients in quarantine after a given number of tests.
Adobe provides a dedicated IP strategy for each customer with a ramp-up IP in order to build a reputation and optimize delivery performance.
IP Certification is a sending best practices program that helps ensuring that emails are received without being blocked by antispam filters or other email blocking systems.
Currently two providers offer IP Certification: Return Path and Certified Senders Alliance.
Certified senders are added to email allowlists which are used by global mailbox providers and email security companies. These commercial allowlists are based on a system that enables the sender to bypass antispam filters altogether or be assigned incremental points as they enter the system.
The Return Path Certification program offers a number of benefits, including the following:
The Certified Senders Alliance Certification offers amongst other benefits:
ISPs are free to use these services and the number of ISPs can vary depending on the allowlist.
However, because more and more ISPs build their antispam filters based on each inbox owner’s behavior rather than analyzing the message content itself, using IP Certification cannot be a guarantee of inbox placement or even delivery.