How to send emails only one by one?

Question

Debian

How to make emails sent only one by one? There is such a problem that one user receives a lot of letters with data that should go one by one and they arrive at the mail service at one moment, but the mail service does not send them evenly, in some there is a delay.
You need to force the mail service to send only because the letters are in the queue

Answer 1

The question is not quite correctly asked - were letters sent from where, with what? From an application? Postal agent? Well, the trouble with the Russian language is urgently back to the 5th grade...
In fact, it is usually possible to force the mail server to send letters one by one, but each mail server has its own settings - see the documentation for your mailer. But I don't think it will help - just a failure to receive one letter (network problem, overload on the server, etc.) is enough and everything will go haywire. If it is important to keep order, do not use email or put serial numbers in letters and "collect" them after receiving them in the right order.