SUMMARY

When running mail servers on cloud platforms, there are some items you need to be aware of, which are specific to the service you are using.

DETAIL

Cloud platforms vary on how you can use SMTP. We've outlined the main issues below we are aware of. Please let us know of any errors, or changes you find so we can update this page.

MICROSOFT AZURE

Microsoft blocks outbound port 25 on the Azure platform unless you have are an Enterprise Agreement user. So you cannot send directly to remote servers (although you can receive), and instead have to route your outbound email through a third party service such as SendGrid. This may introduce an extra cost, and you can see details for the SendGrid option at https://sendgrid.com/.

AMAZON WEB SERVICES (AWS)

By default, outbound SMTP is disabled with AWS, but you can request this unblocked, see https://aws.amazon.com/premiumsupport/knowledge-center/ec2-port-25-throttle/ for details. You may find though that your IP address allocated by AWS is blacklisted, so it is recommended to route your outbound email through another service, which may introduce extra costs.

REFERENCES

Details on sending outbound using Azure can be found at https://docs.microsoft.com/en-us/azure/virtual-network/troubleshoot-outbound-smtp-connectivity

SendGrid for an option to route outgoing emails https://sendgrid.com

MailGun for an option to route outgoing emails https://www.mailgun.com/