I am not sure if I am completely understanding the situation and the suggestion. If Delta Chat works with mail.ru and yandex.ru email accounts, given that you have followed the steps in https://support.delta.chat/t/update-documenation-for-using-mail-ru/4421?u=wofwca, then the feature discussed here (“agent spoofing” / “mimicry”) would be pointless, because everything is already working as well as it can.
I suspect that original post implies that if you just mimic the traffic pattern, then you’ll be able to connect to any mail server in the world and not just the whitelisted ones. I am pretty sure that the only way to do this (given that this has not been patched by the censors yet) is to manipulate TLS SNI, replacing it with yandex.ru / mail.ru, as described in posts around https://ntc.party/t/обход-белых-списков-теория/19123/24.
I personally am not aware of whether this has ever been utilized for IMAP / SMTP and whether this is possible.
For reference, Delta Chat and SNI have been discussed here:
- https://support.delta.chat/t/smtp-tls-handshake-error-login-stuck-on-nine-testrun-org-desktop-windows/4323/4?u=wofwca.
- https://support.delta.chat/t/server-name-indication-sni-extension-during-a-tls-handshake/4463?u=wofwca
If it is possible, I personally doubt that Delta Chat devs are gonna spend resources on this, given how easy it is, in my understanding, for censors to patch this SNI loophole.
In short, I suggest to simply use the “third-party email client setup” approach (described in https://support.delta.chat/t/update-documenation-for-using-mail-ru/4421?u=wofwca and https://providers.delta.chat/yandex-ru), which will let you use Delta Chat and connect with people inside and outside of the country, as long as mail.ru and yandex.ru do deliver your emails to their destinations (so far I am only aware of mail.ru not working with protonmail.com).