In general, BillMax relies on the operating system’s Mail Transfer Agent (MTA) for sending email. Depending on the configuration either Sendmail or Postfix is used. These systems can be configured to send email directly from the BillMax server or email may delivered thru a SMTP relay (typically the mail server for the organization) server.

For performance reasons, direct use of a SMTP connection is not used by BillMax software for sending email. Instead BillMax relies on Sendmail and Postfix MTAs queuing mechanisms to submit batches of emails in an asynchronous manner.

As anti-spam techniques have evolved, sending email properly to ensure delivery has become increasingly difficult to get right. There are quite a few requirements including proper DNS setup, SPF alignment, DKIM authentication, and DMARC reporting. In addition, content rules, IP/domain sending reputation and IP blacklisting also come into play.

Complaints about sent emails not being received by end-customers are almost always due to the email sending infrastructure is configured incorrectly in some way.