Blacksteel Digital · Windows Desktop App

FlashAttach

Personalised Bulk Email, Done Right.

A Windows application that manages contacts, matches personalised attachments, processes PDFs, and sends bulk personalised emails — all from a single window.

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Free demo & full license both available on Gumroad

100% local — no cloud Office 365, Gmail & SMTP Windows 10 / 11 v1.4.0

What is FlashAttach?

Everything your email
workflow needs

FlashAttach is built for professionals and businesses that regularly send personalised bulk emails — invoices, certificates, newsletters, or reports.

Instead of manually attaching the right file to each email, FlashAttach automates the entire workflow: import your contacts, let the app find and match each person's attachment, compose your message once, and send to everyone in a single click.

No cloud dependency

Runs entirely on your machine — works completely offline. No data leaves your network.

Any mail provider

Works with Office 365 (OAuth), Gmail, and any SMTP server.

Smart file matching

Automatically pairs the right attachment to the right contact.

Mail merge

Embed any spreadsheet column as a live field — every email is uniquely personalised.

PDF processing

Split and rename multi-page PDFs into per-contact files automatically.

File encryption

Password-protect attachments as ZIP or AES-256 archives before sending.

Message preview

Preview any recipient's merged subject and email body before the send — catch placeholder issues early.

Email signature

Per-profile signature auto-inserted when you open a new compose — supports merge fields.

Features

Everything in one window

Eight powerful modules covering every step of your personalised email workflow.

📋

Contact Management

Import your contact list in seconds — no manual data entry required.

Import from Excel (.xlsx / .xls) or CSV
Auto column detection for NAME & EMAIL
Editable table: add, edit, delete contacts
Filter contacts without matched attachments

🎯

Smart Attachment Matching

Automatically pair the right file to the right contact — no manual renaming.

Match by name, email address, or both
Starts with, contains, or exact match rules
AND filter: require a keyword (e.g. "2024")
"Same for all" mode for a fixed attachment

✏️

Mail Merge

Every email addresses each recipient personally — name, company, invoice number, or any field.

Insert any column as a live {{placeholder}}
Works in subject line and full HTML body
Live preview of values per recipient
Warning if any placeholder is missing data

📄

PDF Processing Tool

Split a multi-page PDF into individual named files — ready to attach and send.

Split by keyword — ignore blanks or covers
Up to 4 naming keywords for auto filenames
Real-time progress log window
Settings saved between sessions

🚀

Email Sending Engine

Compose once, send personalised emails to your entire contact list.

Plain text or full HTML email body
Preview merged email per-recipient before you send
Live progress bar: sent / total count
Failed emails tracked — retry shows per-recipient failure reasons
Configurable delay to avoid spam filters

🔗

Mail Provider Support

Connect to any mail service — credentials are always secure.

Office 365 via OAuth 2.0 — no password stored
Gmail via App Password (SMTP)
Any SMTP server: host, port, TLS / SSL
Credentials encrypted via Windows Credential Store

👤

Multiple Account Profiles

Manage several mail accounts in one app — switch with a single click.

Up to 3 independent profiles
Mix Office 365, Gmail, and SMTP freely
Each profile keeps its own contacts & drafts
Per-profile email signature auto-inserted when composing
Perfect for multiple brands or departments

🔒

File Encryption

Send sensitive documents safely — password-protect before they leave your machine.

Standard ZIP or AES-256 .7z archives
Set password once per session — auto-applied
Original files are never modified
Ideal for invoices, contracts, payslips

Real-world impact

Your team's morning back

"Our team was sending 200 of these emails one by one. It took most of the day. With FlashAttach the same job is done before the morning coffee."

FlashAttach handles the entire workflow: import contacts, match each person's attachment automatically, personalise every message with mail merge fields, and send to everyone in a single click. The time your team saves on the first run alone justifies the investment.

GDPR & Privacy

Built with privacy by design

FlashAttach is 100% client-side. All processing happens on your local machine — no personal data ever leaves your environment.

100% local processing · no cloud · no SaaS · no third-party data sharing

Fully local

Contact lists, spreadsheets, and email content are processed exclusively on your machine. Nothing is sent to any cloud server.

No data transmission

Emails are dispatched directly from your mail provider. FlashAttach never touches or relays your message content.

OAuth 2.0 sign-in

Office 365 uses OAuth 2.0 device-code flow. The app never sees or stores your Microsoft password — only a short-lived token.

Encrypted credentials

OAuth tokens encrypted with AES-256 stored in the Windows Credential Manager — never in plain text files.

Zero telemetry

No analytics, no usage data, no crash reports. Nothing of any kind is sent from your machine.

You control all data

All stored data lives in %APPDATA%\FlashAttach. Uninstalling prompts you to permanently delete it — full transparency.