[Chyzwar]

> There are no issues with POP and multiple clients whatsoever.

POP3 in standard only have "Leave a copy on the server" but lack synchronisation mechanism.

> I suggest you to educate yourself on DKIM, DMARC, SPF and SMTP before making those statements.

You cannot use SMTP in real world without these protocols. Your messages would automatically land in spam folders of big providers. For example, if you want to send email to Gmail, you need SPF and DKIM [1]. Any half decent implementation of SMTP need to support all these protocols [2].

[1] https://support.google.com/a/answer/81126?hl=en

[2] https://github.com/stalwartlabs/stalwart

> It DOES have delivery tracking. Spam filtering is not a protocol feature and it shouldn't be. I suggest you again to educate yourself.

SMTP have extension for DSNs (Delivery Status Notifications) but crucially it does not provide information if/why email was classified as spam. This is a reason why many website registration form have “check spam folder”. SMTP deliverability is a hard problem both on protocol level and infrastructure on spam filtering[3].

[3] https://blog.paranoidpenguin.net/2020/02/self-hosting-email-...

> If you don't know how to build something doesn't mean it's left out to "hardcore graybeards". You got to admit you just don't know how and either learn or surrender to companies who know, offering the same for a buck. It's pretty simple.

I spend a significant amount of time investigating feasibility of building an email product and build some libraries for email protocols. It is not just my opinion but other HNs users including OP. Search HN for "self hosting email" for others people experience.

[jesterson]

> POP3 in standard only have "Leave a copy on the server" but lack synchronisation mechanism.

Would you explain what do you mean under the "synchronisation mechanism"?

> You cannot use SMTP in real world without these protocols.

You absolutely can. GMail is not the only email provider out there.

> SMTP have extension for DSNs (Delivery Status Notifications) but crucially it does not provide information if/why email was classified as spam. This is a reason why many website registration form have “check spam folder”. SMTP deliverability is a hard problem both on protocol level and infrastructure on spam filtering[3].

I find it hard to even start commenting this, only can suggest you again to educate yourself. Spam related matters were never a part of transport protocol. And never will be for obvious reasons. Just because you would like them to be, it won't change anything.

> I spend a significant amount of time investigating feasibility of building an email product and build some libraries for email protocols. It is not just my opinion but other HNs users including OP. Search HN for "self hosting email" for others people experience.

Happy for you to actually explore building software, but we can't carry discussions just because some HN users carry some, possibly erroneous opinions, or can we?