Comment 6 for bug 670683

I had a more detailed look at phpmailer, and it looks like the idea of using multiple host smtp settings in array (e.g. $cfg->smtphosts = array(array('server' => 'smtp.gmail.com', 'port' => 587, user='someuser', password='somepass'), array(...)) ) will not work unless we do host connectivity valudation outside phpmailer methods. Point is that, while it expects that 'smtphosts' may contain semicolon-separated list of hosts, all other parameters (port if specified separately, username, password, SMTPsecure) are assumed to be the same for all listed hosts (see class.phpmailer.php, line 783 onwards).

Given above, I suggest to leave config.php mail-related parameters as they are now (not extending it to nestled array) and implement mail configuration interface to the current mail settings as we agreed at bug #132474.