As part of our efforts to minimize mail deferrals, we will be deploying a popular and simple technique to combat outbound SPAM i.e disabling Port 25 for MUAs (such as outlook, thunderbird etc).
Port 587 has already been enabled as a replacement and we encourage you to ask your Customers to enable Port 587 for SMTP connections.
To change the SMTP Port you need to enable Port 587 in the following way:
* Outlook: Tools >> Account Settings >> Email >> Change >> More Settings >> Advanced >> Outgoing server (SMTP)
* Thunderbird: Tools >> Account Settings >> Outgoing server (SMTP) >> Edit >> Port
Coupled with SPF and DKIM that we launched earlier, disabling Port 25 will help ensure a more stable and seamless email experience for your Customers.