Problem with : Error using sendmail; Can't send command to SMTP host; Remote host closed connection during handshake

Hi I am trying to sendmail using the below, but i get :

Error using sendmail; Can't send command to SMTP host; Remote host closed connection during handshake

--

mail='#mail@mail';

password='#password';

server = '#smtp.server.com';

Subject = 'Test';

Text = 'Test';

setpref('Internet','E_mail', mail);

setpref('Internet','SMTP_Server', server);

setpref('Internet','SMTP_Username', mail);

setpref('Internet','SMTP_Password', password);

props = java.lang.System.getProperties;

props.setProperty('mail.smtp.port', '587');

props.setProperty('mail.smtp.starttls.enable','true');

sendmail('#mail@mail', Subject, Text)

--

Any ideas what the problem is and how to fix it?

Thank you

[Amanda Fortuna]

Hi,

I'm having the same issue. Did you get this resolved? If so would you mind sharing the resolution please.

Thank you.

[Rajanya]

Hi @Nik, @Amanda Fortuna,

Can you please specify the version of MATLAB that you are using and also the mail server you are trying to establish a connection on? I tried the same code as provided above using outlook smtp server on MATLAB R2024a and did not get any error.

Thanks.

Answer 1

[Samay Sagar]

Hi @Nik, @Amanda Fortuna

My understanding is that the error you are encountering is related to the TLS protocol negotiation failing during the initial SMTP handshake with the email provider SMTP servers.

As mentioned in the MathWorks documentation available here https://www.mathworks.com/help/matlab/ref/sendmail.html ‘sendemail’ supports email servers with Transport Layer Security (TLS) 1.0. However, most email providers no longer support TLS 1.0 .

I have also faced a similar issue in the past. Here’s how I was able to resolve this issue:

1. Download the following JAR file: https://github.com/javaee/javamail/releases/download/JAVAMAIL-1_6_2/javax.mail.jar
2. Rename this JAR file to mail.jar.
3. Replace <matlabroot>/java/jarext/axis2/mail.jar with the downloaded JAR file.
4. Restart MATLAB.
5. Add the following line to your code before using the “sendmail” function:

props.setProperty('mail.smtp.ssl.protocols', "TLSv1.2");

Here’s how your wrapper function should look like:

function sendEmailWrapper(senderEmailAddress, senderPassword, recipientEmailAddress, emailSubject, emailBody)
    mail = senderEmailAddress; 
    password = senderPassword;
    server = 'smtp.server.com'; 
    props = java.lang.System.getProperties;
    props.remove('mail.smtp.socketFactory.class'); 
    props.setProperty('mail.smtp.port', '587');
    props.setProperty('mail.smtp.auth','true'); 
    props.setProperty('mail.smtp.starttls.enable','true'); 
    props.setProperty('mail.debug', 'true');
    props.setProperty('mail.smtp.ssl.protocols', "TLSv1.2");
    setpref('Internet','E_mail', mail); 
    setpref('Internet','SMTP_Server', server); 
    setpref('Internet','SMTP_Username', mail); 
    setpref('Internet','SMTP_Password', password); 
    sendmail(recipientEmailAddress, emailSubject, emailBody);
 end

Please confirm that the DEBUG output from “sendmail” has the following line: "DEBUG: JavaMail version 1.6.2" and NOT 1.4ae.

This should be able to resolve your issue.

Hope this helps!