Design
Email, emailā¦ āCurrently, any beginner user can create their own free email account, just by registering on one of the internet portals,ā claims Wikipedia. Therefore, launching your own mail server seems a bit strange. Nevertheless, I donāt regret the month spent on this, considering it from the day I installed the OS to the day I sent the first email to a recipient on the internet.
Actually, IPTV receivers and the āsingle board computer based on the Baikal-T1 processorā, as well as Cubieboard, Banana Pi, and other devices equipped with ARM microprocessors can be placed alongside āRaspberry Pisā. The āRaspberry Piā was chosen as the most aggressively marketed option. It took several months to find any useful application for this āsingle board computerā. Finally, I decided to launch a mail server on it after reading a science fiction novel about virtual reality shortly before.
āThis is a wonderful vision of the future of the Network,ā Wikipedia reports. It has been 20 years since the first publication. The future has arrived. However, it does not seem wonderful to me without seven thousand subscribers, ten thousand rubles of my site's 'monthly income', etc. This probably pushed me towards 'decentralized social networks' with 'a scarce amount of likes under their (new users - N.M.) posts', registering a domain, and launching my own server.
I am not well-versed in laws. The only thing I know is that a message came to my mobile phone about the need to confirm personal data due to amendments to Federal Law 126-FZ; that's the law I know.
And it turned out that there are as many of these laws as there are mushrooms after rain. If I had continued using free email, I probably wouldnāt have even found out.
āAnd who are we now?ā
Firstly, there is simply no mention of an organizer of the email service in the law. There is an āorganizer of the instant messaging serviceā, but thatās a bit different. The addition āfor personal, family, and household needsā does release this organizer from all duties prescribed by law; however, it still does not cover the organizer that is needed.
Having a guide to Ubuntu Server alongside the law, I suspect that besides chats with their instant messaging, email services (which is obvious) and file servers (which is not so obvious) are intended for "receiving, transmitting, delivering, and (or) processing electronic messages of Internet users."
Development
Compared to other local articles with the hashtag postfix, my creation is certainly quite primitive. Thereās no user authentication, no databases, nor users that arenāt tied to local accounts (the first and third features are in the "minimal mail server"; databases are practically everywhere, just like dovecot).
"Setting up a mail system, in my opinion, is the most complex task in system administration," as one user on Habr very aptly wrote. Following (from ), nevertheless, I missed parts about the alias database, .forward files, and virtual aliases.
However, for ssl/tls, I took 12 configuration lines plus 9 command lines for bash for generating certificates from the dedicated Postfix on CommunityHelpWiki (on the same domain ) (the question remains whether this ssl/tls actually works). Also useful were the firewall in the provider's personal account, nat on the router (I postponed configuring the MikroTik as much as possible; I sent emails by connecting the mail server directly to the cable from the Internet provider), the commands mail, mailq, postsuper -d identifier, the file /var/log/mail.log, the parameter always_add_missing_headers, ptr record information, and finally, the site mail-tester.com (with its simplistic design), which are not mentioned in "mail" articles on Habr, as if they are self-evident.
Before correcting the myhostname parameter value in the /etc/postfix/main.cf file
After correcting the myhostname parameter value in the /etc/postfix/main.cf file
The first email from the Internet provider's technical support taught me that it is not necessary to open emails using the console mail program in order to be able to open and read them with a familiar mail client later. Apparently, this is also not a problem "for beginner admins."
In the comments (to other articles with the hashtag postfix), one user on Habr asks, "let's complicate it a bit, how about web interfaces for different parts and authentication from the database?" For another, "it seems it's really complex for those who haven't tried anything beyond the basics: kernel crashes, security (selinux/apparmor), slightly distributed systemsā¦", and a third writes about the "iRedmail script." You start waiting for the next person to suggest writing about IPv6.
Email services are not spherical horses in a vacuum; they are parts of a wholeāfrom choosing a computer and a domain name to configuring the routerāwhich no manual on setting up an email server can encompass (and in which you probably will never read the theoretical partā , available on the official Postfix website).
As for MikroTik, that's a whole different story.
So that's it. Email has stopped being just a set of console commands, configuration files (including DNS setup), logs, documentation, and hexadecimal numbers instead of Russian letters (according to the koi8-r character table) in the received messages, and has remained a familiar mail client with its protocols imap, pop3, smtp, accounts, incoming and outgoing messages.
Overall, it's externally the same as what email represents when using free email services from the largest IT companies.
Even though it lacks a web interface.
Operation
Still, there's no escaping log review!
I'm eager to inform those who expected to read about the darknet here. Because otherwise, I can only describe what I've found filling the email log of the newly minted server as manifestations of some mysterious darknet, specifically over a couple of days (after connecting directly) with messages about attempts to connect via pop3 under various names from a couple of IP addresses (I mistakenly thought at first that the server was periodically trying to send two emails from the queue, not realizing that my email could suddenly interest someone else on the internet).
The attempts did not cease even after I connected the server through the router. Today's logs are filled with SMTP connections from the same unknown IP address. Nevertheless, I am confident enough not to take any action against this: I hope that even if the username is correctly guessed for email retrieval, the attacker will not be able to figure out the password. I am sure that many will consider this unsafe, just as relying solely on SMTP relay settings and access control in /etc/postfix/main.cf in light of today's attacks.
And they will tear my email protection to shreds.
Source: habr.com
