Or at least that is what google would suggest lol. Either way, you can never have too many docs so an update to specifically call this out when working with SMTP ports would be useful.

But usually, when you encounter UI like above, what it really means is:

TLS -> really means STARTTLS
SSL -> really means TLS

Thanks.

Perhaps it might make sense to add something about that to the email config instructions.

So, instead of

Outgoing Mail (SMTP)
Server: mail.domain.tld
Port: 587 (STARTTLS) or 465 (TLS)

It could say:

Outgoing Mail (SMTP)
Server: mail.domain.tld
Port: 587 (STARTTLS, often just called TLS in app UIs) or 465 (TLS, but often just called SSL in app UIs)

or, less verbose and still pretty confusing given TLS is in both:

Outgoing Mail (SMTP)
Server: mail.domain.tld
Port: 587 (STARTTLS/TLS) or 465 (TLS/SSL)

And maybe linking to your fuller explanation here (or better, put it in the docs and link there) would help too

Although it seems to me that this is basically just a big mess that there isn't too much you can do about given the exact same 3 letters TLS seem to so often mean different things in different places.

• SSL and TLS are both secure connections. Both of these are the same and use certificates. SSL was the name of the old standard. The new standard is called TLS . This distinction of old/new name is something probably only geeks know. Certs are still referred to as "SSL certs" mostly. I guess the term TLS never caught on much (?).

• STARTTLS is a mechanism in some protocols to upgrade an existing unencrypted connection to encrypted. For example, email sending (587) was not encrypted. Commands like DATA/MAIL FROM etc were just sent in plain text. How to make this secure? If you connect blindly as a "secure" encrypted connection, the other end won't understand it. You have to give time for all the worlds servers to upgrade to this secure version. One idea is to make a new port number but then firewalls in the world have to be updated to reflect this. So, they made up a scheme that when the string "STARTTLS" is sent in plain text on port 587, then both sides will start using a TLS connection from that point on. This STARTTLS scheme exists in many protocols including IMAP, ManageSieve etc.

• Finally, app developers don't understand above or they do and think using specific terms is more friendly. So, they will just throw around terms like TLS and SSL. For example, the UI screenshot you posted above is arguably not correct. SSL is some old protocol.

But usually, when you encounter UI like above, what it really means is:

• TLS -> really means STARTTLS
• SSL -> really means TLS

@murgero 587 uses STARTTLS (or TLS here in this case)
465 is SSL, not TLS.

That is not what Cloudron tells me:

( @staff is that a error in the instructions that needs updating then?)

@murgero said in Cannot email my local Calibre books to my Kindle using my Cloudron email credentials:

586 idk if cloudron even uses that.

That was just a typo.

@murgero said in Cannot email my local Calibre books to my Kindle using my Cloudron email credentials:

don't let app configurations confuse you.

It's not app configurations that are confusing me. I realise it's the same as email clients.

What confused me was the config details Cloudron told me to use didn't actually work and appear to be wrong..

However, what does work (thanks you you pointing out that 465 is SSL - not TLS as Cloudron tells me) is using 465 with SSL:

So thank you!

Dunno why I didn't try to try that last night! (actually, I do, because it wasn't what Cloudron was telling me to do it was very late so my brain likely wasn't working properly - yet another reason to start taking getting more and better and more regular sleep more seriously)

Also, whilst 587 with TLS didn't initially work either (temporary name resolution error), when I just tried it again that worked too!

465 is SSL, not TLS.
586 idk if cloudron even uses that.

As far as I know, 2525 is internal for cloudron apps only and requires host mail and no ssl or tls.

Edit: Deleted my other comment cause this one is better.

Edit 2: don't let app configurations confuse you. SMTP is smtp no matter the platform or app. You configure apps the same way you configure your email client (exception being mac which can uses profile xml)