Send email without authentication

This question concerns sending emails from within NC with the admin email address specified in the NC basic settings.

There’s something I don’t understand about the email settings in NC. I have my own domain asdf dot com hosted on lkjh dot com. I set up an email address like

Now, in NC, in the basic settings > email server, I can just type in as the from-address, type in the server address and that seems all I have to do (in fact, it works quite well). How come I don’t have to type in any form of authentication in these settings?

I tried with my hotmail address, just to be sure, and sure enough, outlook dot com won’t let me just use any old address to send emails. That is the behavior I would have expected for any other host’s email address. Why don’t I have to login? Is it just because my NC is hosted on the same host under the same top level domain?

: btw, the domain does exist, but it’s not mine. I took it as an example and left it in there, because it’s funny and you should pay it a visit later.

Well then the smtp server you are connecting to doesn’t require authentication. That’s also known as an Open mail relay. Not something that any mail provider that cares about it’s reputation and reliability in email delivery should be doing nowadays. But hey, who am I to judge others… :wink:

Or did you you maybe use the “Sendmail” option and only provided a “From Address”? This can work depending on how the recieving server is configured, but is also rather unusual to work nowadays, at least with larger providers. If you are sending mails like this, they typically end up in the spam folder or will even be rejected completely.

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I tried both SMTP and SendMail. Both worked.

Is there another way I can test whether another service can send e-mail in my name? I mean, my nextcloud is on the same host and has the same TLD. My obscure webhost might have some obscure setting somewhere that enables sending emails from services within its own boundaries that is not obvious to me. If I could test this with an outside app where I only put in the SMTP server address and the from-address without authentication, sending an e-mail to another address of mine, I could report to my host that this is a rather precarious setup.

Yes, it is quite possible that only certain hosts / IP addresses from the hoster’s network are allowed to send mails.

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Well, thanks for your help. That was revealing and relieving. MX tools says

 550 relay not permitted: you must be authenticated to send messages [231 ms]


Test Result
SMTP TLS OK - Supports TLS.
SMTP Open Relay OK - Not an open relay.

I also tested my NC installation through and it’s looking fine. I believe most of the hard work is done.

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