Source: https://once-email.com/blog/batch-email-attachments-unpackflow

Message safety  · Aug 23, 2026Updated Aug 26, 2026

# Batch-download Email Attachments and Unpack Them Locally with UnpackFlow

Use a dedicated folder, verify every browser download, then list, plan and unpack multipart or nested archives locally without uploading them to an online service.

[Once Email Engineering, Once Email author Once Email Engineering](<https://once-email.com/about>)

Reviewed by Once Email engineering and security review

What this guide helps you do

Download many email attachments and safely organize ordinary, multipart and nested archives on the user’s own computer without uploading them to a third-party unpacking service.

Article guide

Why this article is worth your time

**Original analysis**

This guide separates browser receipt, local archive planning, extraction verification, source cleanup and inbox deletion into independent gates so a partial success cannot erase recovery material.

**Trend context**

Browsers increasingly restrict automatic multiple downloads while multipart and nested archives remain common; local, inspectable processing avoids adding an online upload recipient without weakening archive safety rules.

**Practical value**

Readers can download a batch into one dedicated folder, use the exact UnpackFlow list, plan, run or start workflow, recover from partial failures and clean up only after independent verification.

Use this workflow only after the [attachment safety checklist](<https://once-email.com/blog/attachment-safety-checklist>)  says the files are expected and appropriate to handle. Once Email receives attachment bytes and provides downloads, but it does not preview or unpack files, inspect archive contents, upload them to an online unpacking service, execute included programs or certify them as malware-free.

[UnpackFlow 2.1.9](<https://once-email.com/unpack-flow>)  is a local batch archive tool for Windows, macOS and Linux. It finds ordinary, multipart, nested and self-extracting archives, shows the plan and progress, keeps failed inputs visible, and never uploads the files to Once Email. Start with the [three-platform download and installation page](<https://once-email.com/unpack-flow>) , verify the [v2.1.9 release](<https://github.com/pangxin12345/unpack-flow/releases/tag/v2.1.9>) , or inspect the [open-source repository](<https://github.com/pangxin12345/unpack-flow>)  before using it.

## [1. Download into a new dedicated folder](<https://once-email.com/blog/batch-email-attachments-unpackflow#_1-download-into-a-new-dedicated-folder>)

Create one empty folder for this message or batch. Do not point a recursive tool at your entire Downloads directory. In the message detail, download each attachment or use Download all. Browsers can block multiple automatic downloads and can rename duplicate filenames, so read the per-file result and check the folder itself.

“Bytes received; browser save triggered” means Once Email finished the HTTP response and asked the browser to save it. It does not prove that the browser completed a durable write. Confirm every expected file, size and multipart name before continuing. Keep ` sample.part1.rar ` with later parts and ` .7z.001 ` with ` .7z.002 `; do not rename volumes merely to make them look simpler.

## [2. List and plan before extracting](<https://once-email.com/blog/batch-email-attachments-unpackflow#_2-list-and-plan-before-extracting>)

Replace the conspicuous placeholders generated in the message detail with your dedicated input and a different output folder. Then run ` unpack-flow list '<INPUT>/*' ` and ` unpack-flow plan '<INPUT>/*' `. Quoted wildcards let UnpackFlow choose ordinary archives and valid first volumes without treating later parts as independent jobs.

The plan is evidence about what the local tool can attempt, not a safety verdict. A ` .zip ` extension can be false, a password archive can remain unreadable and a successful plan does not prove that included files are harmless. Stop if the matched scope is broader than the folder you prepared.

## [3. Run in front or start in the background](<https://once-email.com/blog/batch-email-attachments-unpackflow#_3-run-in-front-or-start-in-the-background>)

For a visible foreground job, use the generated ` unpack-flow run -r ... ` command. Recursive mode follows nested archives and writes each input to an isolated result directory without overwriting an existing target. For a long batch, use ` unpack-flow start -r ... `; it returns a task identifier, after which ` unpack-flow status ` reports progress and ` unpack-flow wait ` waits for the final result. The message page displays the exact platform form.

UnpackFlow keeps source archives. It does not automatically execute an EXE inside a package, bypass passwords or silently delete failed inputs. A damaged archive, missing volume, unsupported method, dependency failure or insufficient disk space must remain a visible failure, even when other files succeed.

## [4. Verify results and recover partial failures](<https://once-email.com/blog/batch-email-attachments-unpackflow#_4-verify-results-and-recover-partial-failures>)

Check the exit status, final task state, output directories, file counts and a few representative expected files. Do not interpret “some archives extracted” as “the batch succeeded.” For a missing volume, return to the dedicated download folder and recover that exact attachment. For a damaged or password-protected package, retain every source part and obtain a trusted replacement or an authorised password through a separate channel.

If the browser blocked some downloads, retry only failed items; downloading successful items again can create renamed duplicates and break multipart relationships. If the inbox expired midway, preserve the files already received and do not claim that the missing parts can be recovered from Once Email.

## [5. Clean up and delete separately](<https://once-email.com/blog/batch-email-attachments-unpackflow#_5-clean-up-and-delete-separately>)

Local source cleanup is a new decision after successful verification. Prefer a recoverable trash operation, identify the exact source set and never join cleanup to the first extraction command. Keep sources when any archive is damaged, incomplete, password-protected, unsupported or unverified.

Deleting the temporary inbox is independent. Once Email currently deletes the whole temporary inbox, not one individual message, and a download never triggers deletion. Delete the inbox only after you no longer need server access; deleting it cannot remove local downloads. Likewise, deleting local archives does not remove the email.

This separation—download, list, plan, run or start, verify, local cleanup, then optional inbox deletion—preserves the recovery point at every failure boundary.

## Related guides

A Safe Checklist Before Downloading an Email Attachment

Check the request, sender, file name, type and handling environment before downloading an attachment—and know what email previews and scanners cannot prove.

[A Safe Checklist Before Downloading an Email Attachment](<https://once-email.com/blog/attachment-safety-checklist>)

How to Save Email Test Evidence Without Exposing Secrets

Create useful screenshots, headers and bug reports while removing verification codes, reset tokens, email addresses, identifiers and unrelated personal data.

[How to Save Email Test Evidence Without Exposing Secrets](<https://once-email.com/blog/safe-email-test-evidence>)

Email Alias vs Temporary Inbox vs Permanent Address: Which Should You Use?

Compare forwarding aliases, receive-only temporary inboxes and permanent email accounts by recovery, privacy, replies, record keeping and website policy.

[Email Alias vs Temporary Inbox vs Permanent Address: Which Should You Use?](<https://once-email.com/blog/email-address-types>)

## Use a related tool

Email attachment size budget

Estimate how selected attachments may grow after Base64 and MIME packaging before sending an email.

[Email attachment size budget](<https://once-email.com/tools/attachment-budget>)

[Verification Email Not Arriving? A Safe Troubleshooting Checklist Work through address mistakes, sender delays, retries, filtering and mailbox limits without repeatedly requesting codes or weakening account security.](<https://once-email.com/blog/anxiety>) [Postfix vs Dovecot: Different Roles in a Receiving Email Server See where Postfix and Dovecot sit in the inbound mail path, what each service owns, how LMTP connects them, and which evidence to check when delivery fails.](<https://once-email.com/blog/corecomponent>)