stemlund on "WordPress not sending any emails"

I've used the following settings with WP-Mail-SMTP:

From email: wordpress@iowacityphotobooth.com
From name: Iowa City Photo Booth
Mailer: Send all WordPress emails via SMTP.
SMTP Host: relay-hosting.secureserver.net
SMTP Port: 25
No Encryption
Yes: Use SMTP authentication.
Username: wordpress@iowacityphotobooth.com
Password: my email password

When I send a test email I get the following debugging info... which ends with something about thinking the email is spam or a virus content.

How do I get past this error to successfully using SMTP on my WordPress site?

Test Message Sent

The result was:

bool(true)

The full debugging output is shown below:

object(PHPMailer)#363 (58) {
  ["Priority"]=>
  int(3)
  ["CharSet"]=>
  string(5) "UTF-8"
  ["ContentType"]=>
  string(10) "text/plain"
  ["Encoding"]=>
  string(4) "8bit"
  ["ErrorInfo"]=>
  string(0) ""
  ["From"]=>
  string(32) "wordpress@iowacityphotobooth.com"
  ["FromName"]=>
  string(21) "Iowa City Photo Booth"
  ["Sender"]=>
  string(0) ""
  ["Subject"]=>
  string(45) "WP Mail SMTP: Test mail to stemlund@gmail.com"
  ["Body"]=>
  string(68) "This is a test email generated by the WP Mail SMTP WordPress plugin."
  ["AltBody"]=>
  string(0) ""
  ["MIMEBody:protected"]=>
  string(69) "This is a test email generated by the WP Mail SMTP WordPress plugin.
"
  ["MIMEHeader:protected"]=>
  string(491) "Date: Mon, 10 Jun 2013 14:51:51 +0000
Return-Path: wordpress@iowacityphotobooth.com
To: stemlund@gmail.com
From: Iowa City Photo Booth
Subject: WP Mail SMTP: Test mail to stemlund@gmail.com
Message-ID: <686695d901c3c613882356e38eeb4f39@www.iowacityphotobooth.com>
X-Priority: 3
X-Mailer: PHPMailer 5.2.1 (http://code.google.com/a/apache-extras.org/p/phpmailer/)
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Content-Type: text/plain; charset="UTF-8"

"
  ["SentMIMEMessage:protected"]=>
  string(564) "Date: Mon, 10 Jun 2013 14:51:51 +0000
Return-Path: wordpress@iowacityphotobooth.com
To: stemlund@gmail.com
From: Iowa City Photo Booth
Subject: WP Mail SMTP: Test mail to stemlund@gmail.com
Message-ID: <686695d901c3c613882356e38eeb4f39@www.iowacityphotobooth.com>
X-Priority: 3
X-Mailer: PHPMailer 5.2.1 (http://code.google.com/a/apache-extras.org/p/phpmailer/)
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Content-Type: text/plain; charset="UTF-8"

This is a test email generated by the WP Mail SMTP WordPress plugin.
"
  ["WordWrap"]=>
  int(0)
  ["Mailer"]=>
  string(4) "smtp"
  ["Sendmail"]=>
  string(18) "/usr/sbin/sendmail"
  ["PluginDir"]=>
  string(0) ""
  ["ConfirmReadingTo"]=>
  string(0) ""
  ["Hostname"]=>
  string(0) ""
  ["MessageID"]=>
  string(0) ""
  ["Host"]=>
  string(30) "relay-hosting.secureserver.net"
  ["Port"]=>
  string(2) "25"
  ["Helo"]=>
  string(0) ""
  ["SMTPSecure"]=>
  string(0) ""
  ["SMTPAuth"]=>
  bool(true)
  ["Username"]=>
  string(32) "wordpress@iowacityphotobooth.com"
  ["Password"]=>
  string(12) "password was here"
  ["Timeout"]=>
  int(10)
  ["SMTPDebug"]=>
  int(2)
  ["SMTPKeepAlive"]=>
  bool(false)
  ["SingleTo"]=>
  bool(false)
  ["SingleToArray"]=>
  array(0) {
  }
  ["LE"]=>
  string(1) "
"
  ["DKIM_selector"]=>
  string(9) "phpmailer"
  ["DKIM_identity"]=>
  string(0) ""
  ["DKIM_passphrase"]=>
  string(0) ""
  ["DKIM_domain"]=>
  string(0) ""
  ["DKIM_private"]=>
  string(0) ""
  ["action_function"]=>
  string(0) ""
  ["Version"]=>
  string(5) "5.2.1"
  ["XMailer"]=>
  string(0) ""
  ["smtp:protected"]=>
  object(SMTP)#362 (8) {
    ["SMTP_PORT"]=>
    int(25)
    ["CRLF"]=>
    string(2) "
"
    ["do_debug"]=>
    int(2)
    ["do_verp"]=>
    bool(false)
    ["Version"]=>
    string(5) "5.2.1"
    ["smtp_conn:private"]=>
    resource(289) of type (stream)
    ["error:private"]=>
    NULL
    ["helo_rply:private"]=>
    string(139) "250-p3smtphosting01.prod.phx3.secureserver.net hello [68.178.254.18], secureserver.net
250-HELP
250-SIZE 30000000
250-8BITMIME
250 OK
"
  }
  ["to:protected"]=>
  array(1) {
    [0]=>
    array(2) {
      [0]=>
      string(18) "stemlund@gmail.com"
      [1]=>
      string(0) ""
    }
  }
  ["cc:protected"]=>
  array(0) {
  }
  ["bcc:protected"]=>
  array(0) {
  }
  ["ReplyTo:protected"]=>
  array(0) {
  }
  ["all_recipients:protected"]=>
  array(1) {
    ["stemlund@gmail.com"]=>
    bool(true)
  }
  ["attachment:protected"]=>
  array(0) {
  }
  ["CustomHeader:protected"]=>
  array(0) {
  }
  ["message_type:protected"]=>
  string(5) "plain"
  ["boundary:protected"]=>
  array(3) {
    [1]=>
    string(35) "b1_686695d901c3c613882356e38eeb4f39"
    [2]=>
    string(35) "b2_686695d901c3c613882356e38eeb4f39"
    [3]=>
    string(35) "b3_686695d901c3c613882356e38eeb4f39"
  }
  ["language:protected"]=>
  array(17) {
    ["provide_address"]=>
    string(54) "You must provide at least one recipient email address."
    ["mailer_not_supported"]=>
    string(25) " mailer is not supported."
    ["execute"]=>
    string(19) "Could not execute: "
    ["instantiate"]=>
    string(36) "Could not instantiate mail function."
    ["authenticate"]=>
    string(35) "SMTP Error: Could not authenticate."
    ["from_failed"]=>
    string(35) "The following From address failed: "
    ["recipients_failed"]=>
    string(45) "SMTP Error: The following recipients failed: "
    ["data_not_accepted"]=>
    string(30) "SMTP Error: Data not accepted."
    ["connect_host"]=>
    string(43) "SMTP Error: Could not connect to SMTP host."
    ["file_access"]=>
    string(23) "Could not access file: "
    ["file_open"]=>
    string(33) "File Error: Could not open file: "
    ["encoding"]=>
    string(18) "Unknown encoding: "
    ["signing"]=>
    string(15) "Signing Error: "
    ["smtp_error"]=>
    string(19) "SMTP server error: "
    ["empty_message"]=>
    string(18) "Message body empty"
    ["invalid_address"]=>
    string(15) "Invalid address"
    ["variable_set"]=>
    string(30) "Cannot set or reset variable: "
  }
  ["error_count:protected"]=>
  int(0)
  ["sign_cert_file:protected"]=>
  string(0) ""
  ["sign_key_file:protected"]=>
  string(0) ""
  ["sign_key_pass:protected"]=>
  string(0) ""
  ["exceptions:protected"]=>
  bool(false)
}

The SMTP debugging output is shown below:

SMTP -> FROM SERVER:220 p3smtphosting01.prod.phx3.secureserver.net  ESMTP server ready

SMTP -> FROM SERVER: 250-p3smtphosting01.prod.phx3.secureserver.net hello [68.178.254.18], secureserver.net
250-HELP
250-SIZE 30000000
250-8BITMIME
250 OK

SMTP -> ERROR: AUTH not accepted from server: 500 command unrecognized

SMTP -> FROM SERVER:250 OK

SMTP -> FROM SERVER:250 ok

SMTP -> FROM SERVER:250 ok

SMTP -> FROM SERVER:354 enter mail, end with "." on a line by itself

SMTP -> FROM SERVER:250 merr1l0070QbNh801:LEG:Message dropped for spam or virus content