plugin ":mail:1.0.7" has syntax error on execution - email

Question

mail {
host = "smtp.1und1.de"
port = 465
username = "pt8100853-1"
password = "xxxxxxxx"
props = ["mail.smtp.auth":"true",
"mail.smtp.socketFactory.port":"465",
"mail.smtp.socketFactory.class":"javax.net.ssl.SSLSocketFactory",
"mail.smtp.socketFactory.fallback":"false"]
}
is the contents of config groovy. My controller contains
sendMail {
to "gaby#strotmann.org"
subject "Hello Fred"
body 'How are you?'
}
After activating sendMail I get:
Error 2015-02-25 21:19:25,883 [http-bio-8080-exec-8] ERROR errors.GrailsExceptionResolver - MailSendException occurred when processing request: [GET] /Partner/kommunikation/eMail
Failed messages: com.sun.mail.smtp.SMTPSendFailedException: 501 Syntax error in parameters or arguments
;
nested exception is:
com.sun.mail.smtp.SMTPSenderFailedException: 501 Syntax error in parameters or arguments
. Stacktrace follows:
Message: Failed messages: com.sun.mail.smtp.SMTPSendFailedException: 501 Syntax error in parameters or arguments
;
nested exception is:
com.sun.mail.smtp.SMTPSenderFailedException: 501 Syntax error in parameters or arguments
Line | Method
->> 131 | sendMessage in grails.plugin.mail.MailMessageBuilder
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| 55 | sendMail in grails.plugin.mail.MailService
| 59 | sendMail . in ''
| 165 | doCall in MailGrailsPlugin$_configureSendMail_closure6
| 37 | eMail . . . in org.strotmann.partner.KommunikationController
| 198 | doFilter in grails.plugin.cache.web.filter.PageFragmentCachingFilter
| 63 | doFilter . in grails.plugin.cache.web.filter.AbstractFilter
| 1145 | runWorker in java.util.concurrent.ThreadPoolExecutor
| 615 | run . . . . in java.util.concurrent.ThreadPoolExecutor$Worker
^ 745 | run in java.lang.Thread
I'm somewhat confused to get a syntax error, as I copied the original code directly from the plugin documentation.
How can I escape that problem?