Finding SMTP host and port knowing the e-mail address using JAVA API

Question

I made a simple application to send e-mails using Java API and have a question:

Is there any way to find out the SMTP host knowing the e-mail address of the one who will login to send an e-mail? And also the port?

For example, if the sender's e-mail address is [email protected], the SMTP host is smtp.gmail.com and the port 465. If the sender's e-mail address is [email protected], the SMTP host is smtp.yahoomail.com and the port 25.

Supposing I don't know this, is there any way to find this information using Java API classes? Please note that I'm new to java :)

Thanks in advance,

Andreea

---

Thanks for your answers. I've tried to do the following:

public static String getMXRecordsForEmailAddress(String eMailAddress) { 
          
    String returnValue = null; 
    
    try { 
        String hostName = getHostNameFromEmailAddress(eMailAddress); 
        Record[] records = new Lookup(hostName, Type.MX).run();

        if (records == null) { 
            throw new RuntimeException("No MX records found for domain " + hostName + ".");
        }
         
        // return first entry (not the best solution) 
        if (records.length > 0) { 
            MXRecord mx = (MXRecord) records[0]; 
            returnValue = mx.getTarget().toString(); 
        } 
    } catch (TextParseException e) { 
        throw new RuntimeException(e); 
    } 
         
    System.out.println("return value = "+returnValue);
    return returnValue; 
} 

But, regardless of the value of hostName (eg. gmail.com, yahoo.com ) Record[] records = new Lookup(hostName, Type.MX).run(); always return null.

I'm pretty sure that I missed something, but I don't know what. Will you please help me with this? Can you tell me what I'm doing wrong?

Thank you very much,

Andreea

Answer 1

Unfortunately, there's no standard way to identify the correct outgoing SMTP server for an arbitrary email address, assuming what you're trying to do is let the user specify an email address/password and then send the mail using that account.

That's why email clients (e.g. Thunderbird, Outlook, etc.) generally require the user to configure the outgoing SMTP server name/port manually. You could assist in that process by recognizing a few popular ISPs (Google, Yahoo, etc.) and pre-configuring the proper values, but there's no general-purpose way to do that automatically.