Chapter 20: Jenkins Manual Jobs — Install, Configure and Freestyle

20.15 Archive and email after the build

By Ravindra Bagale · Last updated: 25 October 2026

Why: the problem

When a build finishes, two questions follow. Where is the file it built? And who knows that it finished? If the tgz stays only in the workspace, the next build or the Delete workspace action wipes it, and nobody can redeploy last Tuesday's version during an incident. If nobody is told about a red build, it stays red for days while people keep pushing on top of it. Archive the artifacts and the first problem is solved: Jenkins keeps chosen files with each build, and fingerprints let you trace a file back to the exact build and commit that made it. The Email Extension plugin solves the second: it sends a mail on failure, on fixed, or to the people whose commits are in the build. A Zomato-style on-call team relies on "build fixed" and "build failed" mails to know when they can relax. In this lesson you will archive dist and reports, fingerprint the tgz, run a fake mail server called MailHog in the lab, and send failure and fixed emails you can actually read.

What we will build

You will add Archive the artifacts with dist/.tgz, reports/.xml and build-info.txt and turn on fingerprinting. Then you will start MailHog on the ci network, point Jenkins SMTP settings to it, add Editable Email Notification to badge-api-ci with Failure and Fixed triggers, break and fix a test, and read both emails in the MailHog web page. Last, you will find which build made a given tgz using its MD5 fingerprint.

What: every term in plain English

• Artifact — A file saved with a build, downloadable from its page.
• Fingerprint — An MD5 hash Jenkins records so it can say which builds made or used a file.
• Email Extension — The email-ext plugin with triggers and templates.
• Trigger (email) — When to send: Failure - Any, Fixed, Always and more.
• MailHog — A fake SMTP server that catches mail and shows it in a web page. Lab only.
• SMTP — The protocol for sending mail, usually port 25 or 587; MailHog listens on 1025.

How: step by step

1. Start MailHog

   docker run -d --name mailhog --network ci -p 8025:8025 mailhog/mailhog
   

   What it does: SMTP on mailhog:1025, web on localhost:8025.

   Output

   b2c9...
   

2. Point Jenkins to it

   Manage Jenkins > System > Extended E-mail Notification > SMTP server mailhog > port 1025; also E-mail Notification > SMTP server mailhog > port 1025
   

   What it does: Both mail plugins use MailHog.

   Output

   Saved
   

3. Test mail

   E-mail Notification > Test configuration by sending test e-mail > ravi@lab.local
   

   What it does: A test mail appears at localhost:8025.

   Output

   Email was successfully sent
   

4. Archive files

   badge-api-ci > Post-build > Archive the artifacts > dist/*.tgz, reports/*.xml, build-info.txt > Advanced > Fingerprint all archived artifacts
   

   What it does: Files stay with each build.

   Output

   Saved
   

5. Add email

   Post-build > Editable Email Notification > Recipients ravi@lab.local, dev-team@lab.local > Advanced > Triggers: Failure - Any, Fixed
   

   What it does: Mail on red and on back to green.

   Output

   Saved
   

6. Order

   Put Archive before Email and before Delete workspace
   

   What it does: Archive must run while files exist.

   Output

   Saved
   

Example 1: Email templates that are useful at 2 a

Stack. email-ext, MailHog

Goal. Email templates that are useful at 2 a.m.

Default Subject

$PROJECT_NAME #$BUILD_NUMBER - $BUILD_STATUS

Default Content

Job: $PROJECT_NAME
Build: $BUILD_NUMBER  Status: $BUILD_STATUS
Commit: ${GIT_REVISION, length=7}  Branch: ${GIT_BRANCH}
Changes:
${CHANGES, showPaths=false, format="%a: %m\n"}
Failed tests:
${FAILED_TESTS, showStack=false, maxTests=5}
Log tail:
${BUILD_LOG, maxLines=15}
Open: $BUILD_URL

What each line does

• $BUILD_STATUS — Failure, Fixed, Still Failing and so on.
• ${GIT_REVISION, length=7} — Short commit hash.
• ${CHANGES ...} — Author and message of each commit in the build.
• ${FAILED_TESTS} — Names of failing tests from the JUnit report.
• ${BUILD_LOG, maxLines=15} — The last lines of the log, so you may not need to open Jenkins.
• $BUILD_URL — One click to the build.

Green output

Subject: badge-api-ci #14 - Failure
Job: badge-api-ci
Build: 14  Status: Failure
Commit: a7d3e10  Branch: origin/main
Changes:
ravi: tweak silver threshold
Failed tests:
silver at 500
Log tail:
not ok 2 - silver at 500
Build step 'Execute shell' marked build as failure
Finished: FAILURE
Open: http://localhost:8080/job/badge-api-ci/14/

Expected result. The mail alone tells the on-call person what broke and who changed it. Build #15 sends "Fixed" after the revert.

Example 2: Read the mails from the command line

Stack. MailHog API, Python

Goal. Read the mails from the command line.

read-mail.sh

curl -s localhost:8025/api/v2/messages | python3 -c '
import sys,json
for m in json.load(sys.stdin)["items"][:3]:
    h=m["Content"]["Headers"]
    print(h["To"][0], "|", h["Subject"][0])' 

What each line does

• api/v2/messages — MailHog API with all caught mails.
• Headers To and Subject — Who got which mail.

Green output

dev-team@lab.local | badge-api-ci #15 - Fixed
dev-team@lab.local | badge-api-ci #14 - Failure
ravi@lab.local | Test email #1

Expected result. Proof that failure and fixed mails were sent, without any real mail server.

Example 3: Find the build that made a file

Stack. Jenkins fingerprints

Goal. Find the build that made a file.

which-build.sh

J=http://localhost:8080; A="ravi:$JENKINS_TOKEN"
curl -s -u "$A" -o got.tgz "$J/job/badge-api-ci/lastSuccessfulBuild/artifact/dist/badge-api-1.0.0.tgz"
md5=$(md5sum got.tgz | cut -d" " -f1)
echo "md5 $md5"
curl -s -u "$A" "$J/fingerprint/$md5/api/json?tree=fileName,original[name,number],timestamp" ; echo

What each line does

• artifact/dist/... — Download URL for an archived file.
• md5sum — The fingerprint is the MD5 of the file.
• /fingerprint/MD5/api/json — Jenkins says which job and build made it.

Green output

md5 5e1b0c7f4a3d2e9b8c6a1f0e7d3c2b1a
{"_class":"hudson.model.Fingerprint","fileName":"badge-api-1.0.0.tgz","original":{"name":"badge-api-ci","number":15},"timestamp":1792900000000}

Expected result. Given any tgz on a server, you can find the exact build, and from it the commit.

Verify: did it work?

1. Artifacts listed

   curl -s -u ravi:$JENKINS_TOKEN "http://localhost:8080/job/badge-api-ci/lastSuccessfulBuild/api/json?tree=artifacts[relativePath]"
   

   What it does: Three kinds of files.

   Output

   {"artifacts":[{"relativePath":"build-info.txt"},{"relativePath":"dist/badge-api-1.0.0.tgz"},{"relativePath":"reports/junit.xml"}]}
   

2. MailHog has mail

   curl -s localhost:8025/api/v2/messages | grep -o '"total":[0-9]*'
   

   What it does: Count of mails.

   Output

   "total":3
   

When it is red 1

ERROR: No artifacts found that match the file pattern "dist/*.tgz"

Cause. The build failed before packaging, or the workspace was deleted first.

Fix, step by step

1. Tick "Do not fail build if archiving returns nothing" for failure cases.
2. Put Delete workspace last.

When it is red 2

Connection error sending email ... Could not connect to SMTP host: localhost, port: 25

Cause. SMTP settings still default.

Fix, step by step

1. Set host mailhog and port 1025 in both mail sections.

When it is red 3

No mail on failure

Cause. Trigger list missing Failure - Any, or recipients empty.

Fix, step by step

1. Check Advanced > Triggers.
2. Add Recipient List under each trigger.

Cleanup

1. Remove MailHog

   docker rm -f mailhog
   

   What it does: Stops the fake mail server.

   Output

   mailhog
   

2. Remove download

   rm -f got.tgz
   

   What it does: Cleanup.

   Output

   (no output)
   

Practice tasks

Homework: try at home

Recap

• Archive what you may need to redeploy.
• Fingerprints trace files to builds.
• Email on Failure and Fixed, not on every success.
• MailHog lets you test mail safely.
• Order: archive, publish, email, clean.

FAQ

Should Jenkins store artifacts forever?

No. Push releases to Nexus, Artifactory or S3 and keep few in Jenkins.

Why not mail on every build?

People stop reading. Mail on change of state.

Is MailHog safe for production?

No, it is for labs and tests only.

Where are archived files stored?

Under JENKINS_HOME/jobs/NAME/builds/NUMBER/archive. That is why big artifacts fill the controller disk, and why release files belong in an artifact repository.

Can email include attachments?

Email Extension can attach files with a pattern, but sending a link to the build is usually better than mailing large files.

Interview questions

1. What is artifact fingerprinting?

   Jenkins records MD5 hashes of files to track which builds produced and used them.

2. How do you notify on build failures?

   Email Extension or chat plugins with Failure and Fixed triggers, including commit authors.

3. An old version must be redeployed during an incident. How does Jenkins help?

   Open the last good build, download the archived artifact or use its fingerprint and commit, and run the deploy job with that version, instead of rebuilding from memory.

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