JavaMail SMTP-host error - grails

Question

I have a Grails-application that sends emails. The mailserver has no SMTP-authentication, so it requires "POP before SMTP", which means that I need to authenticate against the POP-account before sending through SMTP. Most often it works, but then once in a while, the mailserver is not picked up from the properties, and it tries to connect to "localhost" instead. Here is the properties:
Properties props = new Properties();
props.setProperty("mail.store.protocol", "pop3")
props.setProperty("mail.pop3.host", "mail.xxxxx.com")
props.setProperty("mail.pop3.port", "110")
props.setProperty("mail.smtp.host", "mail.xxxxx.com")
props.setProperty("mail.smtp.port", "25")
props.setProperty("mail.smtp.sendpartial", "true")
props.setProperty("mail.pop3.socketFactory.port", "110")
props.setProperty("mail.pop3.socketFactory.class","javax.net.SocketFactory")
props.setProperty("mail.pop3.socketFactory.fallback", "false")
Transport t = null
def store
try {
URLName url = new URLName("pop3", "mail.xxxxxxx.com", 110,
"INBOX", "username", "password");
Session session = Session.getDefaultInstance(props, null)
store = session.getStore(url)
store.connect("mail.xxxxxx.com", "username", "password")
Message message = new MimeMessage(session);
message.setFrom(new InternetAddress("xxxx#xxxxxx.com"));
message.setRecipients(Message.RecipientType.TO,
InternetAddress.parse(toAddress, true));
message.setSubject(mailTitle);
message.setContent(messageBody, "text/html");
message.setSentDate(new Date());
t = session.getTransport("smtp")
t.connect()
t.send(message)
return true
}
catch (AddressException e) {
e.printStackTrace()
return false
}
catch (MessagingException e) {
e.printStackTrace()
return false
}
finally {
store?.close()
}
More often than not, this works. But when a Quartz Job is doing the sending, the mailserver entry from the Properties is not honored and it uses "localhost" instead and then fails to send the emails.
I can connect with Telnet and send with the attributes mentioned.
Could it be a timeout issue? According to what I've read in docs, the timeouts are "infinite" as default, so that "should" not be the problem.
Could it be a performance issue? I've created a "dummy app", which - more or less - does the same, but does not issue the sending from a Grails service, but directly from a controller. That one works all the time, but that app is always idleing.
I'm not using the Mail Plugin for Grails, since I couldn't see that it could handle the "pop before smtp"-paradigm.
Thanks in advance.

Answer 1

Solution: It looks as though the solution is to put the "mail.smtp.localhost"-value to the same value as for "mail.smtp.host". Not one single mail has failed since I put that property in. I don't think it was an obvious property to set and an ignorance from my point of view, nevertheless, I hope this will help someone else in the future.
So, my properties are as follows:
Properties props = new Properties();
props.setProperty("mail.store.protocol", "pop3")
props.setProperty("mail.pop3.host", "mail.xxxxxxx.com")
props.setProperty("mail.pop3.port", "110")
props.setProperty("mail.smtp.localhost", "mail.xxxxxxx.com")
props.setProperty("mail.smtp.host", "mail.xxxxxxx.com")
props.setProperty("mail.smtp.port", "25")
props.setProperty("mail.smtp.sendpartial", "true")
props.setProperty("mail.pop3.socketFactory.port", "110")
props.setProperty("mail.pop3.socketFactory.class","javax.net.SocketFactory")
props.setProperty("mail.pop3.socketFactory.fallback", "false")
Setting the value of "mail.smtp.host" to the property "mail.smtp.localhost", not only made the errors go away, the entire routine became a lot faster.
Thank you for your efforts!

Answer 2

props.setProperty("mail.transport.protocol", "smtp");
props.setProperty("mail.smtp.port", "25");
props.setProperty("mail.host", "a.b.com");
props.setProperty("mail.smtp.timeout", "10000");
Above works