Enabling SAPconnect (SMTP) trace 

You may need to enable SAPConnect trace to trouble shoot SMTP related issues or to send it to SAP for analysis.

How to enable SAP Connect  (SMTP) trace?

1. Log into SAP transaction SCOT.

2. Now go to " Utilities" > "Trace" > "Internal Trace " (on SAP Basis Versions lower than 700) , for higher release go to " Utilities" > "Trace Settings".

3. You will get screen as shown below , under section "Switch Trace On/Off"  select the activity you want to trace (Inbound ,outbound or Global) and press enter. 

4.After activating the trace, reproduce the steps which led to the problem or resend the incorrect send request with button "Repeat send" in transaction SOST.

5. Once your activity is done ,switch off the trace , you can view the trace by selection the "Today's" radio button in Display section .(As shown above).

6. Once you press "Display" after selecting appropriate radio button under "Display" section , you will get a list of trace .

7.Select the trace you want to analyze , below is a example of sample trace output .

If you want to send a trace to SAP for analysis, mark the trace in the trace catalog/List and select the menu "Edit > Download Trace". Allocate a <file name>.bin and zip it,then send the file to SAP.

Reference:

https://help.sap.com/saphelp_45b/helpdata/en/08/e043c4c18711d2a27b00a0c943858e/frameset.htm