I would like to get something off my chest.

SMTP is an asynchronous message queueing system.

It is not a reliable asynchronous message queueing system, however you define “reliable”.

Therefore, you should not use it in any step of a process that needs to be reliable.

I think the ICT industry’s PR and marketing with respect to mail and internet access has way outrun its capability, which leads to trouble when clients believe the hype.

Note: the word “asynchronous” did not really contribute much of use in the previous sentences, but I really like using it.