What is on-demand mail relay (ODMR)?

On-Demand Mail Relay (ODMR) is an extension of SMTP (Simple Mail Transfer Protocol) designed for email users who access their email servers from a dynamic IP address or from various locations, often facing the challenge of sending emails that do not get recognized as spam by recipients’ email servers. This situation is typical for users connecting to the internet via dial-up, mobile networks, or VPNs, where their outbound email might be flagged due to the dynamic or ‘foreign’ nature of their IP address compared to the expected, static IP address commonly associated with server-based email sending practices.

ODMR allows these users to send emails through their SMTP server by requesting the server to hold their outgoing mail until they can deliver it from the user’s dynamic or temporary IP address. The email client sends a request to the SMTP server to initiate an SMTP session on demand, effectively making the client’s current IP address temporarily ‘trusted’ for sending email. The process involves client authentication and authorization, ensuring that only legitimate users can request this service.

This mechanism provides a solution that reduces the likelihood of emails being rejected or marked as spam solely based on the IP address they are sent from, without needing to compromise on security measures designed to block unsolicited emails. It’s especially useful for professionals and individuals who need to send reliable and secure emails while on the move, ensuring their communications are received as intended without the drawbacks associated with frequently changing IP addresses.