Nearly everyone has experienced the frustration of sending an email, only to later learn that the recipient never received the message. Unfortunately, it is not uncommon for legitimate messages to be erroneously filtered by spam filters, or dropped altogether.

Non-deliveries can occur for a number of reasons, including mail server DNS configuration errors, poor mail server IP reputation (blacklisting), greylisting, and a host of other pitfalls.

UltraSMTP employs a number of measures to increase the likelihood of messages being successfully delivered to their recipeints.

• Blacklist Monitoring
  Unlike many other SMTP services and webmail services, UltraSMTP is not used for bulk emailing. In fact, we've intentionally structured our service plans to prevent the service from being used for mass emailing. On the contrary - UltraSMTP is designed for individual use with personal mail clients. Because UltraSMTP's mail servers are not used for sending bulk mail or junk mail, our mail servers are unlikely to be blacklisted, and therefore mail sent through our mail servers is less likely to be filtered as junk mail. In addition, we routinely monitor the blacklists used by spam filters. In the event that any of our mail server IP addresses are blacklisted, we immediately address the problem with the blacklist administrator to rectify the problem, and we address the problem with the sender to ensure that it never happens again.
• Greylist Management
  Many receiving mail servers routinely will initially reject a message from a sending mail server as a means for controlling spam. In order to deliver the message, the sending mail server may have to make several retry attempts. UltraSMTP will automatically re-attempt to deliver deferred messages until they are accepted by the receiving mail server.
• DKIM Signing
  Spammers often forge the sending address of messages that they send. Domain Keys Identified Mail (DKIM) is an industry standard for authenticating the sender of a message. It's an outgrowth of an earlier standard, known as DomainKeys, and is based on public key cryptography and digital signatures. Using DKIM, a recipient's mail server can verify that the sender of a message is indeed who it appears to be. UltraSMTP authenticates all outbound messages by signing each message with a DKIM signature keyed to our domain. We can also sign your messages using the DKIM keys for your domain instead of ours, if you wish.
• Feedback Loop (FBL)
  Feedback Loop (FBL) is a standard that is used to alert the sending party when an email is determined to be spam at the receiving end. We are registered for feedback loop service with most of the major email service providers, so that in the event that an email sent through UltraSMTP is marked as spam, we are notified, so that we can take appropriate action.
• Sender Policy Framework (SPF)
  Sender Policy Framework (SPF) is a way of publishing the IP addresses of mail servers that outbound mail for a domain is generally sent from. This provides another way to combat the common practice of spammers spoofing of sender email addresses. SPF records are published as DNS TXT records for a domain. We can assist you in setting up SPF records for your domain upon your request.

Notwithstanding all of the above, SMTP email is inherently not 100% reliable. In spite of all of the above measures, it is possible that a message sent through UltraSMTP (or any SMTP server) goes unreceived by the recipient. To mitigate this inherent problem, UltraSMTP offers a unique set of tools for tracking and confirming delivery of messages after they've been sent, including Delivery Status Notices, Opened Message Alerts, and Document Delivery Confirmation.


Related:

Blacklists, Greylists, IP Reputation, and Spam Filters