Start with the requirement
Choose based on sender identity, recipient scope, client capability, network constraints, volume, and who will operate the solution.
Choose Azure Communication Services Email when
You are building or operating an application-email service, can configure sending domains in Azure, and want Microsoft-hosted SMTP or API delivery that is not tied to one user mailbox. Consult current Azure documentation for availability, quotas, and setup.
Choose smtpify365 when
An existing device or application must send as a specific Microsoft 365 mailbox and exposes only authenticated SMTP settings. The user authorizes delegated Mail.Send access instead of configuring an Azure email resource and sender domain.
They solve different identity problems
Azure Communication Services Email is application infrastructure. smtpify365 is a compatibility bridge to a user mailbox. Compare sender identity, administration, volume, reporting, and support requirements rather than price alone.