Outbound Filtering Hostnames

Available Outgoing Ports

The default and recommended outgoing port is 587 (this supports STARTTLS which will be automatically employed if the connecting server supports it). Port 465 and port 25 can also be utilized for outbound connections, but the likelihood of needing to use these is rare and not recommended.

All outgoing connections require TLS before SMTP AUTH.

Filtering Server Hostnames

These are the hostnames to configure in your Sending MTA/Server. Please refer to your manufacturers documentation on how to configure for your environment:

  • SMTP outbound filter hostname: smtpout.mtaroutes.com (port 587/465/25)

We do not recommend using port 25 for sending outbound mail to the filter.

Regional specific records

These regional specific records are only to be used if you require mail to be received by servers in a specific region.

We do not recommend using these regional records unless absolutely necessary.

Using the below records forces usage of our EU/US/UK/AU/CA/ZA server infrastructure, however deliveries may still be routed via our international platform. Please contact support to force-set your customer ID to EU/US-only delivery servers to ensure messages are not re-routed internationally.

  • EU-only: smtpout-eu.mtaroutes.com (port 587/465/25)
  • US-only: smtpout-us.mtaroutes.com (port 587/465/25)
  • UK-only: smtpout-uk.mtaroutes.com (port 587/465/25)
  • AU-only: smtpout-au.mtaroutes.com (port 587/465/25)
  • CA-only: smtpout-ca.mtaroutes.com (port 587/465/25)
  • ZA-only: smtpout-za.mtaroutes.com (port 587/465/25)

We do not recommend using port 25 for sending outbound mail to the filter.

Connection Limits

The filtering servers by default will accept a maximum of 10 concurrent connections from your servers. This ensures optimal delivery speeds.

To prevent your server from getting temporary rejects "421 Too many concurrent SMTP connections from this IP address; please try again later" and queuing the messages, please ensure you configure your MTA to open a maximum of 10 connections concurrently. This will prevent a backlog building up on your server(s).