have you read it? i considered buying it a while ago but was unsure, quite high price for an ebook that you cannot glimpse into (like with real books at the store some time ago) i thought. Also i learned a “bit” about most of its topics myself long ago.

tricky yes, but very learnable too.

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maybe multiple mail clients are configured to connect to a local server in an office while that server is configured to outside world and also fetches each mail only once. changing of outisde world provider then does not make you reconfigure all mail clients, but only your central once.

i guess step by step was asked for on purpose, but i also don’t know on what level ;-)

@[email protected] :

i’ld suggest as step by step to start small and increase to what you want:

1. register a new account for testing on a freemail service like gmail.com gmx.net , hotmail.com or another. as its just the first step, it does not matter if its google or not, but that you can send and receive emails through it via common protocols like smtp and pop3 and that it is ‘not’ your account you handle important mails with as data losses could occur during experimenting.
2. make sure your freemailer account is configured to use smtp and pop3 for sending/receiving email by a mailclient rather than only through their webpage. some freemailers also need you to have a different password for using the mail client than for logging into their portal (which is good). validate with your mailclient that sending/receiving works with those credentials, and note protocols, port numbers, login mechs maybe discovered by your mailclient.
3. setup your mailserver (mailcow if you like) and connect it to your freemailers account maybe first for sending via smtp (send one to your real mail account) then for receiving maybe via pop3, testing it by sending a mail from your real mail account to the freemailer one.
4. search for a cheap (you are still experimenting, right?) email service where you can use your own domain with, set it up, they likely also have faqs how to do the dns of your domain right to use their MX server. according to https://www.techradar.com/news/best-email-provider NeoMail (https://neo.space/) seems a good choice. i’ld suggest that you get a separate domain for experimenting from a different company (i use name.com) so you are then more aware of how everything works together and also can change parts of it more easily later if needs change. domains are usually cheap like some bucks per year and domain services usually also provide simple ways to define some records like in this case the MX and spf records you need/want for emails to be send to that email service.
5. once you have setup dns records and your mail providers account for sending/receiving mails to/from, try to connect your holy email cow to it and experiment with it. also sending from/to your real mail account, and let it run for a while, look into topics like dmarc and dkim, use spf, dmarc and spf online check tools to see if that setup works as you like. based on your experience you might have ideas then how to go on with it.

spf,dkim and dmarc are good to prevent malicious parties from sending emails in your name to third parties. a mail server works good without that but it is a good practice and might prevent your domain (not your ip) from beeing blacklisted because of spam that you haven’t sent but seems to originate from your domain and cannot be distinguished from your genuine emails only due to the lack of missing spf, dkim and dmarc records. spf and dmarc are dns only settings while dkim are crypto keys you create for signing outgoing emails and the public parts of them are published as dns records again so everyone can check that the signature really comes from your domain. i dont know if or how mailcow supports dkim, but it should be at least possible ;-)

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hm, sounds like literally any regular webhosting service that also offers email (like every such service i know of) to me, then maybe used together with imap (or pop, if you wish), and if you want to connect servers with it to send mails, then “smarthost” or “sattelite system” should be the configuration you are looking for for your own MTA. to get received emails from that service most common is to use pop3 (still common because seemingly every service offers it for compatibility) but other protocols would be faster like immediate recieve using notify within imap, and there are other options too, but those depends on what that service offers like maybe sending your mails once received by them to your own server via smtp or by other protocols depending on what they implemented. i think there is no “twist” with that and -what i understand of what you want - is a quite common thing.

i for myself don’t want 3rd parties to be able to directly read my emails so i run my own mail server as tiny rented VMs from providers while my real emailserver is my homeserver that uses these VMs as “smarthost” and also pulls emails from there immediately. my mailclients are configured to connect to those VMs butbthat connection is relayed through VPN to my homeserver. thus i think my setup is a bit like what you want but i host everything by myself and i don’t use mailcow but it looks like i use the same software mailcow uses too. i guess you are mainly bound to what mailcow offers when limiting yourself to it ;-)