Bag of Mostly Water on "can't send confirmation emails"

a little long but here

The result was:
bool(false)
The full debugging output is shown below:
object(PHPMailer)#319 (69) {
  ["Version"]=>
  string(5) "5.2.7"
  ["Priority"]=>
  int(3)
  ["CharSet"]=>
  string(5) "UTF-8"
  ["ContentType"]=>
  string(10) "text/plain"
  ["Encoding"]=>
  string(4) "8bit"
  ["ErrorInfo"]=>
  string(67) "SMTP Error: The following recipients failed: preston@baxterboyz.com"
  ["From"]=>
  string(23) "info@spartan-gaming.com"
  ["FromName"]=>
  string(4) "info"
  ["Sender"]=>
  string(0) ""
  ["ReturnPath"]=>
  string(0) ""
  ["Subject"]=>
  string(49) "WP Mail SMTP: Test mail to preston@baxterboyz.com"
  ["Body"]=>
  string(68) "This is a test email generated by the WP Mail SMTP WordPress plugin."
  ["AltBody"]=>
  string(0) ""
  ["Ical"]=>
  string(0) ""
  ["MIMEBody":protected]=>
  string(69) "This is a test email generated by the WP Mail SMTP WordPress plugin.
"
  ["MIMEHeader":protected]=>
  string(438) "Date: Fri, 8 Aug 2014 23:28:54 +0000
Return-Path:
To: preston@baxterboyz.com
From: info
Subject: WP Mail SMTP: Test mail to preston@baxterboyz.com
Message-ID:
X-Priority: 3
X-Mailer: PHPMailer 5.2.7 (https://github.com/PHPMailer/PHPMailer/)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

"
  ["mailHeader":protected]=>
  string(0) ""
  ["WordWrap"]=>
  int(0)
  ["Mailer"]=>
  string(4) "smtp"
  ["Sendmail"]=>
  string(18) "/usr/sbin/sendmail"
  ["UseSendmailOptions"]=>
  bool(true)
  ["PluginDir"]=>
  string(0) ""
  ["ConfirmReadingTo"]=>
  string(0) ""
  ["Hostname"]=>
  string(0) ""
  ["MessageID"]=>
  string(0) ""
  ["MessageDate"]=>
  string(0) ""
  ["Host"]=>
  string(9) "localhost"
  ["Port"]=>
  string(2) "25"
  ["Helo"]=>
  string(0) ""
  ["SMTPSecure"]=>
  string(0) ""
  ["SMTPAuth"]=>
  bool(false)
  ["Username"]=>
  string(0) ""
  ["Password"]=>
  string(0) ""
  ["AuthType"]=>
  string(0) ""
  ["Realm"]=>
  string(0) ""
  ["Workstation"]=>
  string(0) ""
  ["Timeout"]=>
  int(10)
  ["SMTPDebug"]=>
  bool(true)
  ["Debugoutput"]=>
  string(4) "echo"
  ["SMTPKeepAlive"]=>
  bool(false)
  ["SingleTo"]=>
  bool(false)
  ["SingleToArray"]=>
  array(0) {
  }
  ["do_verp"]=>
  bool(false)
  ["AllowEmpty"]=>
  bool(false)
  ["LE"]=>
  string(1) "
"
  ["DKIM_selector"]=>
  string(0) ""
  ["DKIM_identity"]=>
  string(0) ""
  ["DKIM_passphrase"]=>
  string(0) ""
  ["DKIM_domain"]=>
  string(0) ""
  ["DKIM_private"]=>
  string(0) ""
  ["action_function"]=>
  string(0) ""
  ["XMailer"]=>
  string(0) ""
  ["smtp":protected]=>
  object(SMTP)#362 (12) {
    ["Version"]=>
    string(5) "5.2.7"
    ["SMTP_PORT"]=>
    int(25)
    ["CRLF"]=>
    string(2) "
"
    ["do_debug"]=>
    bool(true)
    ["Debugoutput"]=>
    string(4) "echo"
    ["do_verp"]=>
    bool(false)
    ["Timeout"]=>
    int(10)
    ["Timelimit"]=>
    int(30)
    ["smtp_conn":protected]=>
    resource(4) of type (stream)
    ["error":protected]=>
    array(3) {
      ["error"]=>
      string(23) "RCPT TO  command failed"
      ["smtp_code"]=>
      string(3) "451"
      ["detail"]=>
      string(58) "4.3.0 : Temporary lookup failure
"
    }
    ["helo_rply":protected]=>
    string(166) "250-server.localdomain
250-PIPELINING
250-SIZE
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN
250-AUTH=PLAIN LOGIN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
"
    ["last_reply":protected]=>
    NULL
  }
  ["to":protected]=>
  array(1) {
    [0]=>
    array(2) {
      [0]=>
      string(22) "preston@baxterboyz.com"
      [1]=>
      string(0) ""
    }
  }
  ["cc":protected]=>
  array(0) {
  }
  ["bcc":protected]=>
  array(0) {
  }
  ["ReplyTo":protected]=>
  array(0) {
  }
  ["all_recipients":protected]=>
  array(1) {
    ["preston@baxterboyz.com"]=>
    bool(true)
  }
  ["attachment":protected]=>
  array(0) {
  }
  ["CustomHeader":protected]=>
  array(0) {
  }
  ["lastMessageID":protected]=>
  string(53) ""
  ["message_type":protected]=>
  string(5) "plain"
  ["boundary":protected]=>
  array(3) {
    [1]=>
    string(35) "b1_e9b3ff4008aeaa399bc0d2123cdefe21"
    [2]=>
    string(35) "b2_e9b3ff4008aeaa399bc0d2123cdefe21"
    [3]=>
    string(35) "b3_e9b3ff4008aeaa399bc0d2123cdefe21"
  }
  ["language":protected]=>
  array(18) {
    ["authenticate"]=>
    string(35) "SMTP Error: Could not authenticate."
    ["connect_host"]=>
    string(43) "SMTP Error: Could not connect to SMTP host."
    ["data_not_accepted"]=>
    string(30) "SMTP Error: data not accepted."
    ["empty_message"]=>
    string(18) "Message body empty"
    ["encoding"]=>
    string(18) "Unknown encoding: "
    ["execute"]=>
    string(19) "Could not execute: "
    ["file_access"]=>
    string(23) "Could not access file: "
    ["file_open"]=>
    string(33) "File Error: Could not open file: "
    ["from_failed"]=>
    string(35) "The following From address failed: "
    ["instantiate"]=>
    string(36) "Could not instantiate mail function."
    ["invalid_address"]=>
    string(15) "Invalid address"
    ["mailer_not_supported"]=>
    string(25) " mailer is not supported."
    ["provide_address"]=>
    string(54) "You must provide at least one recipient email address."
    ["recipients_failed"]=>
    string(45) "SMTP Error: The following recipients failed: "
    ["signing"]=>
    string(15) "Signing Error: "
    ["smtp_connect_failed"]=>
    string(22) "SMTP connect() failed."
    ["smtp_error"]=>
    string(19) "SMTP server error: "
    ["variable_set"]=>
    string(30) "Cannot set or reset variable: "
  }
  ["error_count":protected]=>
  int(2)
  ["sign_cert_file":protected]=>
  string(0) ""
  ["sign_key_file":protected]=>
  string(0) ""
  ["sign_key_pass":protected]=>
  string(0) ""
  ["exceptions":protected]=>
  bool(true)
}
The SMTP debugging output is shown below:
SMTP -> get_lines(): $data was ""SMTP -> get_lines(): $str is "220 server.localdomain ESMTP Postfix
"SMTP -> get_lines(): $data is "220 server.localdomain ESMTP Postfix
"SMTP -> FROM SERVER:220 server.localdomain ESMTP Postfix
CLIENT -> SMTP: EHLO spartan-gaming.com
SMTP -> get_lines(): $data was ""SMTP -> get_lines(): $str is "250-server.localdomain
"SMTP -> get_lines(): $data is "250-server.localdomain
"SMTP -> get_lines(): $data was "250-server.localdomain
"SMTP -> get_lines(): $str is "250-PIPELINING
"SMTP -> get_lines(): $data is "250-server.localdomain
250-PIPELINING
"SMTP -> get_lines(): $data was "250-server.localdomain
250-PIPELINING
"SMTP -> get_lines(): $str is "250-SIZE
"SMTP -> get_lines(): $data is "250-server.localdomain
250-PIPELINING
250-SIZE
"SMTP -> get_lines(): $data was "250-server.localdomain
250-PIPELINING
250-SIZE
"SMTP -> get_lines(): $str is "250-ETRN
"SMTP -> get_lines(): $data is "250-server.localdomain
250-PIPELINING
250-SIZE
250-ETRN
"SMTP -> get_lines(): $data was "250-server.localdomain
250-PIPELINING
250-SIZE
250-ETRN
"SMTP -> get_lines(): $str is "250-STARTTLS
"SMTP -> get_lines(): $data is "250-server.localdomain
250-PIPELINING
250-SIZE
250-ETRN
250-STARTTLS
"SMTP -> get_lines(): $data was "250-server.localdomain
250-PIPELINING
250-SIZE
250-ETRN
250-STARTTLS
"SMTP -> get_lines(): $str is "250-AUTH PLAIN LOGIN
"SMTP -> get_lines(): $data is "250-server.localdomain
250-PIPELINING
250-SIZE
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN
"SMTP -> get_lines(): $data was "250-server.localdomain
250-PIPELINING
250-SIZE
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN
"SMTP -> get_lines(): $str is "250-AUTH=PLAIN LOGIN
"SMTP -> get_lines(): $data is "250-server.localdomain
250-PIPELINING
250-SIZE
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN
250-AUTH=PLAIN LOGIN
"SMTP -> get_lines(): $data was "250-server.localdomain
250-PIPELINING
250-SIZE
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN
250-AUTH=PLAIN LOGIN
"SMTP -> get_lines(): $str is "250-ENHANCEDSTATUSCODES
"SMTP -> get_lines(): $data is "250-server.localdomain
250-PIPELINING
250-SIZE
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN
250-AUTH=PLAIN LOGIN
250-ENHANCEDSTATUSCODES
"SMTP -> get_lines(): $data was "250-server.localdomain
250-PIPELINING
250-SIZE
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN
250-AUTH=PLAIN LOGIN
250-ENHANCEDSTATUSCODES
"SMTP -> get_lines(): $str is "250-8BITMIME
"SMTP -> get_lines(): $data is "250-server.localdomain
250-PIPELINING
250-SIZE
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN
250-AUTH=PLAIN LOGIN
250-ENHANCEDSTATUSCODES
250-8BITMIME
"SMTP -> get_lines(): $data was "250-server.localdomain
250-PIPELINING
250-SIZE
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN
250-AUTH=PLAIN LOGIN
250-ENHANCEDSTATUSCODES
250-8BITMIME
"SMTP -> get_lines(): $str is "250 DSN
"SMTP -> get_lines(): $data is "250-server.localdomain
250-PIPELINING
250-SIZE
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN
250-AUTH=PLAIN LOGIN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
"SMTP -> FROM SERVER:250-server.localdomain
250-PIPELINING
250-SIZE
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN
250-AUTH=PLAIN LOGIN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
CLIENT -> SMTP: MAIL FROM:
SMTP -> get_lines(): $data was ""SMTP -> get_lines(): $str is "250 2.1.0 Ok
"SMTP -> get_lines(): $data is "250 2.1.0 Ok
"SMTP -> FROM SERVER:250 2.1.0 Ok
CLIENT -> SMTP: RCPT TO:
SMTP -> get_lines(): $data was ""SMTP -> get_lines(): $str is "451 4.3.0 : Temporary lookup failure
"SMTP -> get_lines(): $data is "451 4.3.0 : Temporary lookup failure
"SMTP -> FROM SERVER:451 4.3.0 : Temporary lookup failure
SMTP -> ERROR: RCPT TO  command failed: 451 4.3.0 : Temporary lookup failure