I know Prosody does & I’d put money on ejabberd supporting it too but I’ve not looked it up. You can check compliance for Conversations using https://compliance.conversations.im/ which includes message archive management + carbons or use a client that exposes a servers supported XEPs. Yes, it works with encrypted messages.
https://xmpp.org/extensions/xep-0203.html
I’ve not yet had issues with messages not getting delivered when recipient is offline.
Which server do you use that caches messages for you, and how do I know if a given XMPP provider has implemented this functionality?
Also, does it also work with e2ee messages?
I know Prosody does & I’d put money on ejabberd supporting it too but I’ve not looked it up. You can check compliance for Conversations using https://compliance.conversations.im/ which includes message archive management + carbons or use a client that exposes a servers supported XEPs. Yes, it works with encrypted messages.