[johannes1234321]

E-Mail isn't trustworthy. You may get a confirmation that an initial SMTP server accepted a mail, but that's it. There's also no good way to detect that an endpoint (receiver address) is gone for good to stop sending messages.

You will probably point me to SMTP success messages, but a removed mailbox might only be known by a backend server.

Also mail infrastructure will potentially include heavy spam filters etc. making it quite inconvenient. Not even mentioning security aspects with limited availability of transport layer encryption with proper signatures.

[vidarh]

What you're saying is true of public e-mail infrastructure, but that's besides the point. As a queuing solution internally in a system you can make it as resilient as you like with ease because there's a huge ecosystem of resilient software you can use for it.

Same goes for security - your objection is true for public e-mail delivery without additional requirements on the servers or clients, but that is not relevant for a private infrastructure.

[johannes1234321]

In a private environment you have tons of options. The post however refers to notification between independent entities on the public network.

[vidarh]

Running over the public internet does not mean you rely on unknown third party mail servers. If I address a message to [e-mail], only the servers configured to handle mail for apiendpoint.mycustomer.com and my sending server is involved in the exchange. And that is if you trust MX records for this exchange rather than have the customer input the address of the receiving SMTP server directly.