How to make an smtp server?

Question

Debian

Good evening.
Due to the expanding fleet of servers, a problem has arisen. The SMTP server of the provider is often heavily clogged and reports from the servers often do not come, so I want to install a local server to send letters, but I haven’t come across anything decent on the Internet. There is debian and hardware, but the trouble is with the software. Another port 25 is required open, since security cameras refuse to send through another.
Thanks everyone

Answer 1

The main candidates are postfix and exim. Which one to choose is more a matter of taste.
How exactly to configure in your particular case, the documentation will tell you.

Answer 2

Recently, he moved away from monsters like exim and posfix, and switched to https://opensmtpd.org Config lines 10-15 with comments, can both proxy and distribute, and keeps the queue. Just for applications such as sending mail from application sites and forwarding further to the destination.
For example, in one closed place I use it as a local mail deliverer to users and forward the necessary items outside. Elsewhere, as a smart host on multiple sites.

Answer 3

Ask Google about the smtp server
Read about the settings of certain
Select
Download
Install and configure
PROFIT!