I have configured the SMTP options using my mail server.
In the encoding SMTP options I selected the "disabled" option (I use the spanish version so the name may be different).
The connection to the mailserver is fine and I'm able see the communication logs, but I can't send mails, I'm having this error:

SMTP connect() failed. github.com/PHPMailer/PHPMailer/wiki/Troubleshooting

Trazado de la salida del SMTP:

2016-10-06 18:32:30

SERVER -> CLIENT: 220 Cas1 Microsoft ESMTP MAIL Service ready at Thu, 6 Oct 2016 15:32:30 -0300 2016-10-06 18:32:30

CLIENT -> SERVER: EHLO feedback.arnaldocastro.com.uy 2016-10-06 18:32:30

SERVER -> CLIENT:

250-Cas1 Hello [10.100.100.30]

250-SIZE 36700160

250-PIPELINING

250-DSN

250-ENHANCEDSTATUSCODES

250-STARTTLS

250-X-ANONYMOUSTLS

250-AUTH NTLM LOGIN

250-X-EXPS GSSAPI NTLM

250-8BITMIME

250-BINARYMIME

250-CHUNKING

250 XRDST 2016-10-06 18:32:30

CLIENT -> SERVER: STARTTLS 2016-10-06 18:32:30

SERVER -> CLIENT: 220 2.0.0 SMTP server ready 2016-10-06 18:32:30	SMTP Error: Could not connect to SMTP host. 2016-10-06 18:32:30	CLIENT -> SERVER: QUIT 2016-10-06 18:32:30

SERVER -> CLIENT: 2016-10-06 18:32:30

SMTP ERROR: QUIT command failed: 2016-10-06 18:32:30

SMTP connect() failed. 
    github.com/PHPMailer/PHPMailer/wiki/Troubleshooting
 

As you can see I've remarked the line which I believe is the problem, the client (limesurvey) is starting the communication with TLS despite I have not selected SMTP TLS encode option.
Any ideas of how can I resolve this problem?, thanks in advance.

accsa wrote: As you can see I've remarked the line which I believe is the problem, the client (limesurvey) is starting the communication with TLS despite I have not selected SMTP TLS encode option.

This looks like an issue in the PHPMailer library.

Opportunistic TLS
PHPMailer 5.2.10 introduced opportunistic TLS - if it sees that the server is advertising TLS encryption (after you have connected to the server), it enables encryption automatically, even if you have not set SMTPSecure. This might cause issues if the server is advertising TLS with an invalid certificate, but you can turn it off with $mail->SMTPAutoTLS = false;.

What version/build of LimeSurvey is used? What version of PHP is used?

I wonder why you want to deactivate TLS. The used mailserver supports TLS encryption as my tests showed.
You might need to change the hostname or the port. Normally I would go for TLS and 465. StartTLS is a bit wacky, since it can be tricked into not encrypting at all. StartTLS is on Port 25.

Thanks for answering.
Now I'm using the last version of Limesurvey 2.53+161004. I was using Versión 2.06+ with the same configuration and it was working OK.
I have installed a new server and I updated the version, so I don't know if is something with the new server or with the new version. At the moment I still having the old server (Windows 2012) with version 2.06 working OK just for test, and the new server (CentOS 7).
The PHP version on my new server is PHP 5.6.26 (cli) (built: Sep 17 2016 09:53:52)

I've tried TLS and SSL configurations with port 25, 587 and 465 with no success, now I don't use TLS in order to simplify things avoiding to have certificates problems, on the other hand the communication is internal, so I don't need to encrypt it.

I agree with you, it sounds like a PHPMailer or similar problem but I'm stuck.

Please check if SELinux is active on CentOS 7. If yes, disable it.
blog.zwiegnet.com/linux-server/disable-selinux-centos-7/

Since PHP 5.6 certificates get checked on names. If the mailservers hostname and certificate aren't matching it can be the issue too.
You can deactivate this behavior in PHP. Not a good idea.
php.net/manual/en/migration56.openssl.php
Sometimes the CentOS CA bundle is not having all CAs. So even a valid certificate isn't validated by CentOS OpenSSL correctly.

I still don't get how you use the mailserver internally. You state "communication is internal". Is the mailserver under you control too?
How can you be sure with the routing when using the hostname, which I can reach too?

I currently cannot recommend a way to config the phpmailer in the LimeSurvey installation.

Asked the developers how to change the configuration of the phpmailer.
Answer from LouisGac was, that i should read the code. So, feel free to open a bugreport or read the code.

Ok, chatted a bit around.
Next release of LS will have "Opportunistic TLS" disabled. So you might just wait for the next release and just update to fix your issue.

OK, thanks for your help, I'm trying a couple of things.
I will post the results as soon as I can.

accsa wrote: OK, thanks for your help, I'm trying a couple of things.

Perhaps you first try the update.

LimeSurvey 2.54 build 161007

-Fixed issue: TLS handshake used even if no TLS is set in SMTP settings

accsa wrote: I have configured the SMTP options using my mail server.
In the encoding SMTP options I selected the "disabled" option (I use the spanish version so the name may be different).
The connection to the mailserver is fine and I'm able see the communication logs, but I can't send mails, I'm having this error:

SMTP connect() failed. github.com/PHPMailer/PHPMailer/wiki/Troubleshooting

Trazado de la salida del SMTP:

2016-10-06 18:32:30

SERVER -> CLIENT: 220 Cas1 Microsoft ESMTP MAIL Service ready at Thu, 6 Oct 2016 15:32:30 -0300 2016-10-06 18:32:30

CLIENT -> SERVER: EHLO feedback.arnaldocastro.com.uy 2016-10-06 18:32:30

SERVER -> CLIENT:

250-Cas1 Hello [10.100.100.30]

250-SIZE 36700160

250-PIPELINING

250-DSN

250-ENHANCEDSTATUSCODES

250-STARTTLS

250-X-ANONYMOUSTLS

250-AUTH NTLM LOGIN

250-X-EXPS GSSAPI NTLM

250-8BITMIME

250-BINARYMIME

250-CHUNKING

250 XRDST 2016-10-06 18:32:30

CLIENT -> SERVER: STARTTLS 2016-10-06 18:32:30

SERVER -> CLIENT: 220 2.0.0 SMTP server ready 2016-10-06 18:32:30	SMTP Error: Could not connect to SMTP host. 2016-10-06 18:32:30	CLIENT -> SERVER: QUIT 2016-10-06 18:32:30

SERVER -> CLIENT: 2016-10-06 18:32:30

SMTP ERROR: QUIT command failed: 2016-10-06 18:32:30

SMTP connect() failed. 
    github.com/PHPMailer/PHPMailer/wiki/Troubleshooting
 

As you can see I've remarked the line which I believe is the problem, the client (limesurvey) is starting the communication with TLS despite I have not selected SMTP TLS encode option.
Any ideas of how can I resolve this problem?, thanks in advance.

i have problem with mail sender unable to send any mail..Please help me!
I use version 2.53+161004.
Unable to send with smtp, crone, of any kind i try...

Excelent!! it works like a charm! with the same configuration now it works perfectly.
To be honest I didn't expect an update so quick, that why I'd said I was going to test a couple of things.
It's good to have this formu, thanks again for your help.

ibro123:
Do you have any log of the error? what are you using to send mails, your own mail server or an account from other parties?