Log POP, IMAP and SMTP Traffic in Mozilla Thunderbird

Updated August 23, 2016

Logging is for the industrious developer alone—and for the curious user, of course. In addition to finding out what's going on behind the scenes of email exchanges in Mozilla Thunderbird yourself (especially if that which is going on is not going right), you can help those helping you with problems enormously if you're able to send them a log of what's happening when you try to send or receive mail.

Turning on transaction logging may not be straight forward an affair, but it is not difficult either.

Log POP, IMAP and SMTP Traffic in Mozilla Thunderbird

To create a log file with all POP (Post Office Protocol), SMTP (Simple Mail Transfer Protocol) or IMAP (Internet Message Access Protocol) traffic in Mozilla Thunderbird:

Now, on Windows:

  • Select All Programs | Accessories | Command Prompt from the Start menu.
  • Type "set NSPR_LOG_MODULES=" followed immediately by
    • "POP3:4" for POP,
    • "IMAP:4" for IMAP and
    • "SMTP:4" for SMTP logging.
  • Press Enter.
    • You can enable logging for multiple protocols by separating them with commas (',').
    • To log both POP and SMTP traffic, for example, type "set NSPR_LOG_MODULES=POP3:4,SMTP:4" (excluding the quotation marks).
    • To log only IMAP traffic, type "set NSPR_LOG_MODULES=IMAP:4", for instance.
  • Type "set NSPR_LOG_FILE=%HOMEDRIVE%%HOMEPATH%\Desktop\tbird_log.txt".

On Mac OS X:

  • Open a Terminal window.
  • Type "export NSPR_LOG_MODULES=" followed immediately by
    • "POP3:4" for POP,
    • "IMAP:4" for IMAP and
    • "SMTP:4" for SMTP  logging
  • Press Enter.
    • You can enable logging for multiple protocols by separating them with commas (',').
    • To log both POP and SMTP traffic, for example, type "export NSPR_LOG_MODULES=POP3:4,SMTP:4" (excluding the quotation marks).
    • To log only IMAP traffic, type "export NSPR_LOG_MODULES=IMAP:4", for instance.
  • Type "export NSPR_LOG_FILE=~/Desktop/tbird.log".
  • Press Enter.
  • Now type "/Applications/Thunderbird.app/Contents/MacOS/thunderbird-bin".
  • Press Enter again.
  • Perform the desired email actions in Mozilla Thunderbird.
  • Quit Mozilla Thunderbird and take a look at "tbird.log" on your Desktop.

On Linux:

  • Open a Terminal window.
  • Type "export NSPR_LOG_MODULES=" followed immediately by
    • "POP3:4" for POP,
    • "IMAP:4" for IMAP and
    • "SMTP:4" for SMTP logging.
  • Press Enter.
    • You can enable logging for multiple protocols by separating them with commas (',').
    • To log both POP and SMTP traffic, for example, type "export NSPR_LOG_MODULES=POP3:4,SMTP:4" (excluding the quotation marks).
    • To log only IMAP traffic, type "export NSPR_LOG_MODULES=IMAP:4", for instance.
  • Type "export NSPR_LOG_FILE=~/tbird.log.txt".
  • Press Enter.
  • Type "thunderbird".
  • Press Enter again.
  • Perform the desired email actions in Mozilla Thunderbird.
  • Quit Mozilla Thunderbird and take a look at "tbird.log.txt" in your Home directory.

    Turn Logging Off in Mozilla Thunderbird

    Traffic logging is enabled only for the session you start from the command line. You do not have to turn it off.