I have libnet 3.11 which is the current latest version. I have an SMTP server which requires TLS and LOGIN auth. I can manually get all this to work fine with openssl s_client and manual commands up to the STARTTLS and then the AUTH LOGIN without problems. With perl Net::SMTP_auth, the AUTH LOGIN immediately closes the connection with a 421 error without returning prompts for the base 64 username/password. I cannot work out why. Something in the environment changed as this was working until recently, I suspect some SMTP server change. The TLS part is fine and the server enforces this before auth. I am using Net::SMTP_auth instead of Net::SMTP as the server does not advertise AUTH mechanisms which makes Net::SMTP fail to do authentication as it thinks the server can't do it. Manual: 
openssl s_client -starttls smtp -crlf -connect smtpserver:25
.
.
.
250 OK
AUTH LOGIN
.
.
.
334 VXNlcm5hbWU6

[download]
This is all fine and working as expected - code 334 is the username prompt. However, with: 
my $smtp = Net::SMTP_auth->new('smtpserver');
$smtp->starttls;
$smtp->auth('LOGIN', 'username', 'password);

[download]
This dies with an SMTP 421 code "Connection closed" in the ->auth method. Debugging with Net::Cmd shows that this dies before it gets a username prompt and occurs immediately after sending "AUTH LOGIN".

In reply to Net::SMTP_auth giving 421 errors with authentication by philkime

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.