Hello.
In version 5.2.4 practically impossible configure SMTP emailing without encryption.
If set login/pass, Projeqtor always enable encryption, nowise show this in the interface; this is very not trivial and it is just flat out confusing. This brings to that sort of errors, without any words of reason and status of enabled tls:
2016-03-02 20:37:37.531 ***** ERROR ***** Error sending mail
2016-03-02 20:37:37.532 ***** ERROR ***** SMTP Server : 10.0.1.1
2016-03-02 20:37:37.532 ***** ERROR ***** SMTP Port : 25
2016-03-02 20:37:37.532 ***** ERROR ***** Mail stored in Database : #21
2016-03-02 20:37:37.532 ***** ERROR ***** PHPMail error : SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting
2016-03-02 20:37:37.532 ***** ERROR ***** PHPMail debug :
Search of the forum not give result for me:
babynus wrote: Ssl is not mandatory, just default if authentication is set and no protocolecspecified.
To specify other protocole, just enter it before host name :
tls://hostname
Sorry, but this is explained in the user manual.
RTFM 
babynus wrote: TLS uses (in standard) port 587
Port 465 is for SSL protocole.
If you dont specify protocole in host definition, protocole will be guessed from port
25 : standard smtp (not encrypted)
465 : SSL
587 : TLS
If you want to force TLS (for instance if you use TLS on a non standard port) ust specify it on host definition
smtp server : tls://mail.xxx.xx
In contrast to forum's message above, in the .ppt manual explain what tls uses by default for 25 port. But not describe how to disable encryption.
I do not know php, but i am found two way to solve it:
1. Define the server address with ' ://' in config/parameters.php. This is not work if try set it in "Global parameters" page, probably, because the first char space removed at writing to base.
$paramMailSmtpServer = ' ://address';
2. Fix this bug in a projeqtor.php.
if ($paramMailSmtpUsername and $paramMailSmtpPassword) {
$phpmailer->SMTPAuth = true; // Enable SMTP authentication
$phpmailer->Username = $paramMailSmtpUsername; // SMTP username
$phpmailer->Password = $paramMailSmtpPassword; // SMTP password
$phpmailer->SMTPSecure = 'tls'; // default (for ports 25 and 587
if ($paramMailSmtpPort == '465')
$phpmailer->SMTPSecure = 'ssl'; // 465 is default for ssl
if (strpos ( $phpmailer->Host, '://' )) {
$phpmailer->SMTPSecure = substr ( $phpmailer->Host, 0, strpos ( $phpmailer->Host, '://' ) );
$phpmailer->Host = substr ( $phpmailer->Host, strpos ( $phpmailer->Host, '://' ) + 3 );
}
}
Replace line 947
if (strpos ( $phpmailer->Host, '://' )) {
to, for example
if (strpos ( $phpmailer->Host, '://' ) !== false) {
In that case to be work '://address' and setting on а "Global parameters" page. But, again, the user is not possible to guess this way is turned off encryption..
Thank for a projeqtor.
P.S.
line 936, // $phpmailer->SMTPDebug=1;
->
2016-03-02 20:37:37.532 ***** ERROR ***** PHPMail debug :
P.S.2
Lacking a button to send a test email to verify your settings. (Like a redmine/openproject)