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Thanks @girish that worked! Seems the only thing I did different was turning off STARTTLS in the SMTP section.
and also thank you @marcusquinn for letting me know all the other options that are better. At this stage I'm just sort of playing around and testing things out to try and get them to work, and seeing how they work.
Hello!
I'm trying to enable Nextcloud to receive email using the mail server with my Cloudron instance. I'm pretty new to all of this stuff so hopefully what I am trying to do is even possible 
It seems Nextcloud is sending email ok for other purposes, but I can't connect to the mail client internal to Nextcloud to receive email. I have enabled incoming email, and a few mailboxes, in the mail server settings on Cloudron. I then used the details provided under the link "use these settings" in the incoming email section on Cloudron to fill in the boxes here:
I removed the details from the screenshot, but you can see the error I got at the bottom when I clicked Connect. It says "Unexpected error during account creation."
The documentation for a lot of this stuff seems a little out of date and inaccurate in relation to maybe some new interface changes on Cloudron's side... It could be that I haven't really enabled incoming email, but it appears I have. This is also true for Cloudron's documentation for Nextcloud email config here https://cloudron.io/documentation/apps/nextcloud/#email
I'm confused why its referring to Rainloop. Am I not able to access the Cloudron email server from Nextcloud directly? Or I need to install Rainloop as like middleware on my Cloudron instance? It says that Rainloop is a Nextcloud app, but I don't see it in the list of options on my current instance... It seems this is the email client they are promoting now, just called "mail", and its the one I took the screenshot of above while trying to configure.
https://apps.nextcloud.com/apps/mail
Is cloudron's own user management system more robust than say the one in NextCloud? If I run a NextCloud instance inside of a Cloudron instance, can I use Nextcloud's user management to manage cloudron users? Would this even make sense?
If I understand correctly, Cloudron can interface using LDAP... Is there FLOSS user management system that is recommended when there is a need for more sophisticated user management across multiple systems? (including systems outside of a cloudron, for example)
I'm sorta at my learning edge here, so pardon any questions that seem strange to answer.
Thanks! A couple more questions came up from your reply @nebulon
So if Cloudron is using an external LDAP system, then that becomes where users are managed from? or you can use both a LDAP and Cloudron's user management system at the same time?
Can I have multiple domains pointing at the same Cloudron server? Does Cloudron deal with something like this itself? or I would need something like nginx/caddy to deal with that? Can I so something more sophisticated like let someone log into what's effectively the same Cloudron server from different domains, but the domain that they choose to log in from determines what user, or facet of a user, they then interact in Cloudron with? (Maybe this is where the group system you mentioned could come in too?)
I'm not really sure how to ask all this, I've seen the power of Cloudron, but not sure how to think about using it so that I don't set myself up for failure later.
All Cloudron apps work well together I guess? If I just have one server, it will be fine to use any Cloudron app with any other right?
In what cases should I consider using 2+ servers rather than one? Can one Cloudron manage multiple servers? i.e. I log into one my.domain.org (for example) , but really Cloudron has access to more than one server underneath.
Or is it better to run Cloudron with just one server? I'm guessing if I host it with something like a digitalocean droplet, then I can just upgrade my droplet as I need more resources and both Cloudron+DO gracefully adjust to each other?
I would think in some cases though it would be better to have multiple servers (if this is possible, please share links for how to set this up), for example, maybe having a server totally dedicated to something like a Matrix/Riot instance (so that its as fast a possible), and then have another server maybe for something like NextCloud. Please correct me if I am wrong... I guess there is also the question of cost, and whether one big server, or multiple servers dedicated to specific use-cases would optimize both cost and performance.
The other question I have is about user-management. I understand that Cloudron has its own system... But can other systems take over that role of user management from Cloudron? What are the recommended alternatives here for someone wanting to orchestrate something on the level of like multiple schools in a school system... and providing each of those groups with something like a SSO experience, but with a different set of tools made available in each case. (maybe this more abstract user management + auth is what would be used to span multiple Cloudron servers and give me that Holistic experience even if Cloudron can't do that entirely itself across multiple servers?)
I ask these questions because I am trying to set up a system that would let me do something like a school system, but where the "schools" are more like small informal learning groups who coalesce around a topic of interest, and then pull together a minimal set of tools to enable them to learn together in their domain of interest. Part of the point would be then to teach them how to self-host their own tools (likely on Cloudron too if thats how I'm learning to do it), so in some ways, my primary Cloudron instance would be more like a big sandbox for these groups to come learn and play in, with the intention of later leaving to their own space, and hopefully finding a way to federate.
Any help/advice here would be appreciated, even if its not related to something specific I asked above.
Hello! I'm new, so forgive my naive questions... But I was reading the article below about how to Use Cloudron as an OAuth 2 provider, but my self-hosted cloudron doesn't have an API access menu. What am I missing?
