I also had some issues with emails when I made the very first initial setup (I use SMTP).
The main issue I've found is the lack of server side logging of what was actually happening.
I've seen that q2a 1.6.2 uses PHPMailer version 2.0.4 that does not offer any debug options (I think it uses this "old" version to mantain backward compatibility with more php versions).
The more recent PHPMailer version (5.2.7) has some good debug options, so I decided to "upgrade" my q2a installation to use this version (even if I do not like the practice of modifying the core of a product that I use, since I could have in the future more work to do in the upgrading to a higher release...).
I replaced the 2 following classes :
with those found here :
(class.phpmailer.php, class.smtp.php, renaming them with prefix "qa-")
There are also a couple of lines that must be modified in the qa-class.phpmailer.php (I do not explain it here, but if needed I can give the details).
Now I have the possibility of logging everything that happens when the PHPMailer is invoked passing a couple of debug parameters when the PHPMailer is instantiated in the :
The parameters are :
$mailer->Debugoutput = "error_log";
$mailer->SMTPDebug = 2;
Debugoutput available options are : "echo" or "error_log"
SMTPDebug available options are : 0 = off, 1 = commands, 2 = commands and data
In production you tipically put "0" (2 is very verbose....)
Hope it helps.....