Logging POP, IMAP, and SMTP email traffic isn’t just for the industrious developer. If you want to see what’s going on behind the scenes of your email exchanges in Mozilla Thunderbird (especially if what’s going on is not going right), logging yields lots of information that can help you or your tech-support person diagnose the problem.

Turning on transaction logging may not be a straightforward affair, but it is not difficult, either. To create a log file with all Post Office Protocol, Simple Mail Transfer Protocol, and Internet Message Access Protocol traffic in Mozilla Thunderbird, first, make sure it’s not running. Then, follow the instructions for your operating system.

Turning on Transaction Logging in Windows

In Microsoft Windows, follow this procedure:

  • Open the Command Prompt.
  • Press Win+X and click Command Prompt to open the Command Prompt.
  • Type
  • set NSPR_LOG_MODULES=
  • followed immediately by:
  • POP3:4 for POP loggingIMAP:4 for IMAP loggingSMTP:4 for SMTP logging
  • Enable logging for multiple protocols by separating them with commas. For example:
  • To log both POP and SMTP traffic, type:
  • set NSPR_LOG_MODULES=POP3:4,SMTP:4
  • To log only IMAP traffic, type:
  • set NSPR_LOG_MODULES=IMAP:4
  • Press Enter.
  • Type
  • set NSPR_LOG_FILE=%HOMEDRIVE%%HOMEPATH%\Desktop\tbird_log.txt
  • Press Enter.
  • Type
  • start thunderbird
  • Press Enter again.
  • Perform the desired email actions in Mozilla Thunderbird.
  • Quit Mozilla Thunderbird and open tbird_log.txt on your Desktop.

Turning on Transaction Logging in macOS

Use the following procedure on your Mac:

Open the Command Prompt.

Press Win+X and click Command Prompt to open the Command Prompt.

Type

set NSPR_LOG_MODULES=

followed immediately by:

  • POP3:4 for POP loggingIMAP:4 for IMAP loggingSMTP:4 for SMTP logging

Enable logging for multiple protocols by separating them with commas. For example:

To log both POP and SMTP traffic, type:

set NSPR_LOG_MODULES=POP3:4,SMTP:4

To log only IMAP traffic, type:

set NSPR_LOG_MODULES=IMAP:4

Press Enter.

set NSPR_LOG_FILE=%HOMEDRIVE%%HOMEPATH%\Desktop\tbird_log.txt

start thunderbird

Press Enter again.

Perform the desired email actions in Mozilla Thunderbird.

Quit Mozilla Thunderbird and open tbird_log.txt on your Desktop.

  • Open a Terminal window.
  • Type
  • set NSPR_LOG_MODULES=
  • followed immediately by:
  • POP3:4 for POP loggingIMAP:4 for IMAP loggingSMTP:4 for SMTP logging
  • Press Enter.
  • Enable logging for multiple protocols by separating them with commas. For example:
  • To log both POP and SMTP traffic, type:
  • export NSPR_LOG_MODULES=POP3:4,SMTP:4
  • To log only IMAP traffic, type:
  • export NSPR_LOG_MODULES=IMAP:4
  • Type
  • export NSPR_LOG_FILE=~/Desktop/tbird.log
  • Press Enter.
  • Type
  • /Applications/Thunderbird.app/Contents/MacOS/thunderbird-bin
  • Press Enter again.
  • Perform the desired email actions in Mozilla Thunderbird.
  • Quit Mozilla Thunderbird and find tbird.log on your Desktop.

Turning on Transaction Logging in Linux

In Linux, follow this procedure:

Open a Terminal window.

export NSPR_LOG_MODULES=POP3:4,SMTP:4

export NSPR_LOG_MODULES=IMAP:4

export NSPR_LOG_FILE=~/Desktop/tbird.log

/Applications/Thunderbird.app/Contents/MacOS/thunderbird-bin

Quit Mozilla Thunderbird and find tbird.log on your Desktop.

  • Open a Terminal window.
  • Type
  • set NSPR_LOG_MODULES=
  • followed immediately by:
  • POP3:4 for POP loggingIMAP:4 for IMAP loggingSMTP:4 for SMTP logging
  • Press Enter. Enable logging for multiple protocols by separating them with commas. For example, type:
  • export NSPR_LOG_MODULES=POP3:4,SMTP:4
  • to log both POP and SMTP traffic and
  • export NSPR_LOG_MODULES=IMAP:4
  • to log only IMAP traffic.
  • 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 review 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.

Press Enter. Enable logging for multiple protocols by separating them with commas. For example, type:

to log both POP and SMTP traffic and

to log only IMAP traffic.

Type 

export NSPR_LOG_FILE=~/tbird.log.txt

Press Enter.

thunderbird

Press Enter again.

Quit Mozilla Thunderbird and review tbird.log.txt in your Home directory.

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