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Importing Large MBOX File

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I'm trying to import a 7.5GB MBOX file that I exported from Thunderbird using ImportExport Tools. A smaller MBOX file (1.52 GB) imported great, but the larger one isn't working. ePADD recognizes the correct message amount, but, while processing, moves directly from "starting to process" to "reading names, identifying locations" and zero messages are actually imported. I've already re-imported the file into Thunderbird to confirm the MBOX file isn't corrupted. Any ideas?


asked Mar 10, 2016 by Kevin
reshown Jan 2, 2018 by Josh_Schneider

1 Answer

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Hi Kevin,

  1. How many messages do you have in the 7.5GB mbox file? (ePADD can handle 250,000 messages at this moment. We will be able to handle 750,000 messages by Oct. 2018 [end date of our IMLS grant)
  2. Have you tried using emailchemy to import the email messages in Thunderbird and output the messages from emailchemy to "standard mbox file"? Some conversion program don't output "standard mbox" file. So far,we have no problem importing mbox files from emailchemy.


answered Mar 10, 2016 by Peter_Chan (2,770 points)

Hi Peter,

Thank you for the quick reply

  1. There are about 62,000 messages in the email inbox, so that doesn't appear to be the issue.
  2. I haven't purchased emailchemy quite yet, but thank you for the recommendation! Looks like it might be more reliable than ImportExportTools. With that said, the 1.52 GB MBOX file imported into ePADD just fine, and it was also created using ImportExportTools. Is there a way to verify whether an MBOX file is standard or not? I ran the file through FIDO but the output was inconclusive.


I am not aware of any tool to verify "standard" mbox file. Could you send me the log? It would be even better if you can share the file with me (

Thank you for taking time to help! I'll reach out via email with more documentation on Monday.


ePADD is a software package developed by Stanford University's Special Collections & University Archives that supports archival processes around the appraisal, ingest, processing, discovery, and delivery of email archives.