The following code can be added to event like AfterAppInit. It assumes that you have a table named smtp_settings that stores several sets of SMTP settings as different parts of your projects ( modules ) may have a different set of SMTP settings.
string strEmailKey = "WebPortal"; // module name
dynamic data;
dynamic rs = DB.Query("select * from smtp_settings where module ='" + strEmailKey + "'");
if (data = rs.fetchAssoc())
{
GlobalVars.runnerProjectSettings["security"]["emailSettings"]["SMTPUser"] = data["SMTPUser"];
GlobalVars.runnerProjectSettings["security"]["emailSettings"]["SMTPServer"] = data["SMTPServer"];
GlobalVars.runnerProjectSettings["security"]["emailSettings"]["SMTPPort"] = data["SMTPPort"];
GlobalVars.runnerProjectSettings["security"]["emailSettings"]["SMTPPassword"] = data["SMTPPassword"];
GlobalVars.runnerProjectSettings["security"]["emailSettings"]["fromEmail"] = data["fromEmail"];
GlobalVars.runnerProjectSettings["security"]["emailSettings"]["securityProtocol"] = 0; // no SSL or TLS
}