linux sendmail doesn't work (stat=deferred)

Question

I have set up an linux webserver on my raspberry pi and now want the server be able to send emails without configuring a complete mailserver.

Thats why I have chosen the MTA 'sendmail', which I'm trying to configure correctly for days now.

In my /etc/mail/sendmail.mc I have added these lines:

define(`SMART_HOST',`[smtp.strato.de]')dnl
define(`RELAY_MAILER_ARGS', `TCP $h 465')dnl
define(`ESMTP_MAILER_ARGS', `TCP $h 465')dnl
define(`confAUTH_OPTIONS', `A p')dnl
TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
FEATURE(`authinfo',`hash -o /etc/mail/authinfo/auth.db')dnl

In my hashed /etc/mail/authinfo/auth I have

AuthInfo: "U:root" "I:[email protected]" "P:mypassword"

But sending a test email like this

echo "Just testing my sendmail relay" | mail -s "Sendmail Relay" [email protected]

doesn't give me any errors but still never arrived the recipient.

Let's check my /var/log/mail.log

Mar 30 14:35:02 localhost sm-mta[2375]: v2UCKHOT002349: to=<[email protected]>, ctladdr=<[email protected]> (0/0), delay=00:14:45, xdelay=00:02:00, mailer=relay, pri=300405, relay=smtp.strato.de. [81.169.145.133], dsn=4.0.0, stat=Deferred: Connection reset by smtp.strato.de.
Mar 30 14:35:02 localhost sm-mta[2375]: v2UAPG9t014829: to=<[email protected]>, ctladdr=<[email protected]> (0/0), delay=02:09:46, xdelay=00:00:00, mailer=relay, pri=1380405, relay=smtp.strato.de., dsn=4.0.0, stat=Deferred: Connection reset by smtp.strato.de.
Mar 30 14:35:02 localhost sm-mta[2375]: v2UAHJSs014703: to=<[email protected]>, ctladdr=<[email protected]> (0/0), delay=02:17:43, xdelay=00:00:00, mailer=relay, pri=1470405, relay=smtp.strato.de., dsn=4.0.0, stat=Deferred: Connection reset by smtp.strato.de.

What does stat=Deferred: Connection reset by smtp.strato.de. mean?

What can I do to finally solve my sending-email-problem?

I'm thankful for any hint!

Solution

I think I solved my problem by

1. Using port 587 instead of 465, thanks to the hint of Andrzej
2. Specifying the sender mail, because my hoster strato was denying mails that are not authenticated (in my case [email protected])

So, sending a test mail with this command worked

mail -s "Some random subject" -a "From: [email protected]" [email protected]

Don't forget to send the final mail by hitting [ctrl] + [d]