Over time, Internet service providers (ISPs) have come up with methods for filtering and rejecting emails to deal with the increasing volume of unwanted commercial email (spam). This can sometimes interfere with the delivery of email from legitimate senders due to inadvertently using the wrong phrase or server configuration. To address these types of problems, Lyris has delivered a set of features and best practices to maximize the possibility of getting email delivered.
Deliverability Improvements
Before version 10, ListManager used a very simplistic method for detecting bounces. It used the numeric bounce codes returned by mail servers; all bounces were treated as equivalent. Beginning with version 10, ListManager parses the textual message (SMTP response text) returned from mail servers. Response messages are broken down into a number of categories, with each requiring different behavior. Here are some of the basic categories:
Invalid user: When ListManager sees a response code that corresponds to this category, the email address is put on hold server-wide immediately.
Filtered Content: Content that trips a spam filter or has other characters that cause it to be rejected (e.g., the message size is too large).
Technical Issues: The destination server is consistently busy or otherwise unavailable.
Banned IP: The IP address sending the email has been banned, typically for excessive complaints or for attempting to email too many invalid users at that domain
Transient Failures: The destination mailbox is temporarily unavailable (usually because it is full).
Dynamic Deliverability
Besides indicating the status of the recipient, the SMTP response text is often used to relay other information back to the sender. Typical messages can be paraphrased as “you have too many simultaneous connections to our servers” or “too many messages sent per connection opened." In such cases, ListManager dynamically adjusts its behavior to accommodate the sending characteristics signaled by the destination server; this maximizes deliverability and keeps sending speed as high as possible.