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I installed Postfix & Dovecot on Debian.

Then I tried using SMTP authentication according to this guide:

Unfortunately the following test tails:

telnet localhost 25
auth plain <base64 encoded usernaem/password>

We get a "535 5.78 Error: authentication failed:"

in var/log/mail.warn we habe a new line which is: "warning: localhost[]: SASL PLAIN authentication failed:"

unfortunately it does not say what is wrong. Any ideas?

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It's really stupid. But here is the reason what went wrong:

we generated the base 64 string according to the documentation:

echo -ne '\000username\000password' | openssl base64

unfortunately our password started with a number. After changing the password to start with a character it worked fine!

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