Message transfer agent architecture for email delivery systems

An email delivery system providing an email delivery service comprising:

• a memory;
• and
• one or more processors configured to perform processing, the processing comprising:
• executing, by the email delivery system, a message transfer agent (MTA) and a proxy server;
• selecting, by the MTA, from a message queue, a first email message for processing, wherein the message queue comprises a plurality of email messages received from a plurality of senders, the plurality of senders corresponding to a plurality of subscribers of the email delivery service;
• determining, by the MTA, a sender associated with the first email message;
• determining, by the MTA, a recipient for the first email message;
• identifying, by the MTA and based upon the sender determined for the first email message, a plurality of source internet protocol (IP) addresses comprising IP addresses usable as source IP addresses for the first email message;
• selecting, by the MTA, a particular source IP address from the plurality of source IP addresses;
• determining, by the MTA, a destination IP address for the recipient of the email message;
• identifying, by the MTA and from a set of one or more proxy servers, a particular proxy server that is configured to handle the selected particular source IP address;
• communicating, by the MTA and to the particular proxy server, information including the particular source IP address and the destination IP address;
• and
• transmitting, by the MTA, the first email message to the destination IP address using a connection established by the proxy server between the particular source IP address and the destination IP address.

A non-transitory computer-readable medium having program code that is stored thereon, the program code executable by one or more processing devices for performing operations comprising:

• executing, by an email delivery service, a message transfer agent (MTA) and a proxy server;
• selecting, by the MTA, from a message queue, a first email message for processing, wherein the message queue comprises a plurality of email messages received from a plurality of senders, the plurality of senders corresponding to a plurality of subscribers of the email delivery service;
• determining, by the MTA, a sender associated with the first email message;
• determining, by the MTA, a recipient for the first email message;
• identifying, by the MTA and based upon the sender determined for the first email message, a plurality of source internet protocol (IP) addresses comprising IP addresses usable as source IP addresses for the first email message;
• selecting, by the MTA, a particular source IP address from the plurality of source IP addresses;
• determining, by the MTA, a destination IP address for the recipient of the email message;
• identifying, by the MTA and from a set of one or more proxy servers, a particular proxy server that is configured to handle the selected particular source IP address;
• communicating, by the MTA and to the particular proxy server, information including the particular source IP address and the destination IP address;
• and
• transmitting, by the MTA, the first email message to the destination IP address using a connection established by the proxy server between the particular source IP address and the destination IP address.