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The Spark Mail project contains code for a tutorial on how Apache Spark could be used to analyze email data. As data we use the Enron Email dataset from Carnegie Mellon University. We show how to ETL (Extract Transform Load) the original file-per-email dataset into Apache Avro and Apache Parquet formats and then explore the email set using Spark.

Building the project

The Spark Mail project uses an sbt build. See for how to download and install sbt.

Then from mail-spark directory:

# build "fat" jar with classes and all dependencies under 
# mailrecords-utils/target/scala-2.11/mailrecord-utils-{version}-fat.jar
sbt assembly

ETL (Extract Transform Load)

The original dataset does not lend itself to scalable processing. The file set has over 500,000 small files. This would create over 500,000 input splits/initial partitions. Furthermore, we don't want our analytic code to have to deal with the parsing.

Therefore we parse the input once and aggregate the emails into the following MailRecord format in Apache Avro IDL:

protocol MailRecordProtocol {

  record Attachment {
    string mimeType;
    bytes data;

  record MailRecord {
    string uuid;
    string from;
    union{null, array<string>} to = null;
    union{null, array<string>} cc = null;
    union{null, array<string>} bcc = null;
    long dateUtcEpoch;
    string subject;
    union{null, map<string>} mailFields = null;
    string body;
    union{null, array<Attachment>} attachments = null;

For convenience the Java MailRecord and Attachment classes generated from the MailRecord Apache Avro IDL file were copied under mailrecord-utils/src/main/java/com/uebercomputing/mailrecord/ and

If you wanted to update the original AVDL file and regenerate new Java files, use the following to build. This requires Apache Maven. To build this dependency and publish it to your local Maven repository (default ~/.m2/repository) do the following:

git clone
cd spark-mailrecord
mvn clean install

# Update current Java definitions in spark-mail
cp -R spark-mailrecord/src/main/java/com spark-mail/mailrecord-utils/src/main/java

Enron Email Dataset

Note to Windows Users

The Enron email dataset used (see below) contains files that end with a dot (e.g. ~/maildir/lay-k/inbox/1.).

The unit tests used actual emails from this dataset. This caused problems for using Git from Eclipse. Checking the source code out from command line git works.

However, on Windows these Unit tests fail because the files ending with . were not processed correctly.


Renamed the test files with a .txt extension. That fixes the unit tests. However, to process the actual files in the Enron dataset (see below) we need to rename each file with a .txt extension. Note: Don't use dots as the end of a file name!!!

Obtaining/preparing the Enron dataset describes the Enron email dataset and provides a download link at

This email set is a gzipped tar file of emails stored in directories. Once downloaded, extract via: > tar xfz enron_mail_20150507.tar.gz (or use tar xf as new tar autodectects compression)

This generates the following directory structure:

  • maildir
    • $userName subdirectories for each user
    • $folderName subdirectories per user
      • mail messages in folder or additional subfolders

This directory structure contains over 500,000 small mail files without attachments. These files all have the following layout:

Message-ID: <31335512.1075861110528.JavaMail.evans@thyme>
Date: Wed, 2 Jan 2002 09:26:29 -0800 (PST)
Subject: Kelly Webb
<Blank Line>
Message Body

Some headers like To, Cc and Bcc or Subject can also be multiline values.

Parsing Enron Email set into Apache Parquet binary format

This data set at 423MB compressed is small but using the default small files format to process this via FileInputFormat creates over 500,000 splits to be processed. By doing some pre-processing and storing all the file artifacts in Apache Avro records we can make the analytics processing more effective.

We parse out specific headers like Message-ID (uuid), From (from) etc. and store all the other headers in a mailFields map. We also store the body in its own field.

Avro Parser

The mailrecord-utils mailparser enronfiles Main class allows us to convert the directory/file-based Enron data set into one Avro file with all the corresponding MailRecord Avro records. To run this class from the spark-mail root directory

> mailrecordUtils/console
val mailDir = "/datasets/enron/raw/maildir"
val avroOutput = "/datasets/enron/mail.avro"
val args = Array("--mailDir", mailDir,
                 "--avroOutput", avroOutput)

Parquet Parser

To generate an Apache Parquet file from the emails run the following:

> mailrecordUtils/console
val mailDir = "/datasets/enron/raw/maildir"
val parquetOutput = "/datasets/enron/mail.parquet"
val args = Array("--mailDir", mailDir,
                 "--parquetOutput", parquetOutput)

Using Parquet format, we can easily analyze using our local spark-shell. All examples use the Parquet format. To use a DataFrame with Avro see

val mailDf ="/datasets/enron/mail.parquet")
 |-- uuid: string (nullable = true)
 |-- from: string (nullable = true)
 |-- to: array (nullable = true)
 |    |-- element: string (containsNull = true)
 |-- cc: array (nullable = true)
 |    |-- element: string (containsNull = true)
 |-- bcc: array (nullable = true)
 |    |-- element: string (containsNull = true)
 |-- dateUtcEpoch: long (nullable = true)
 |-- subject: string (nullable = true)
 |-- mailFields: map (nullable = true)
 |    |-- key: string
 |    |-- value: string (valueContainsNull = true)
 |-- body: string (nullable = true)
 |-- attachments: array (nullable = true)
 |    |-- element: struct (containsNull = true)
 |    |    |-- fileName: string (nullable = true)
 |    |    |-- size: integer (nullable = true)
 |    |    |-- mimeType: string (nullable = true)
 |    |    |-- data: binary (nullable = true)

val doraMailsDf = mailDf.where($"from" === "")

Spark Analytics

  • See spark-mail/analytics/dataset and spark-mail/analytics/rdd for Scala code.

Exploring via Jupyter with Apache Toree Scala notebooks

  • Copy notebooks from spark-mail/notebooks to /home/jovyan/work to make them available from Docker notebook

  • See Docker documentation at for install on your OS

  • We will be using the latest jupyter/all-spark-notebook which ran Spark 2.4.0 as of Nov 24, 2018

    • Adjust your local Spark standalone to match the all-spark-notebook version or
    • Check out and adjust pyspark-notebook Spark/Hadoop and then load from adjusted all-spark-notebook locally.
  • The bash script below assumes that:

    • SPARK_HOME environment variable points to the base of your Spark installation
    • adjust to your local IP address (don't use localhost - non-routable from Docker container)
  • Shared local directories with same dirs on host machine as in Docker image

    • /dataset/enron - is the local dir containing your data files (e.g. enron-small.parquet)
      • Spark driver runs on Docker machine
      • Executor runs on Docker host machine
    • /home/jovyan/work - directory containing notebook(s) to load (Jupyter notebook on Docker image runs from /home/jovyan)
docker pull jupyter/all-spark-notebook

# For "local" standalone Spark cluster with master/executor on local machine
# Download Spark 2.4.0 for Hadoop 2.7 from
# Untar, set $SPARK_HOME to spark-2.4.0-bin-hadoop2.7 dir
$SPARK_HOME/sbin/ --host
$SPARK_HOME/sbin/ spark://

# See "Connecting to a Spark Cluster in Standalone Mode" at 
docker run -p 8888:8888 -v /datasets/enron:/datasets/enron \
   -v /home/jovyan/work:/home/jovyan/work \
   --net=host --pid=host -e TINI_SUBREAPER=true \
   -e SPARK_OPTS='--master=spark:// --executor-memory=8g' \


Tutorial on parsing Enron email to Avro and then explore the email set using Spark.







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