When sending email with SMTPTransporter class, a “connection broken” error may be encountered. When this occurs, it is advisable to enable the SMTP log. To do this, execute the following line:

SET DATABASE PARAMETER(SMTP Log;1)

This will start generating log file (named “4DSMTPLog.txt”) for low-level communications between 4D and the SMTP server. With this logging, it can be determined if the initial connection was successful at all, and if so, when that connection was broken during the communication. This is usually indicated by the log line “SMTP Connection closed” along with a timestamp.