How do I attach a file to a reply in my inbox?
Short answer: open the conversation in your Unified Inbox, start your reply, then either click the paperclip in the reply box or drag the files straight onto the conversation. You can attach up to 5 files, up to 10 MB each, with about 11 MB of files in total per reply. Attachments work on replies you send from your inbox — they are deliberately not available on campaign or cold outreach emails, and that difference is the most important thing on this page.
A worked example: a prospect writes back asking for your pricing sheet. You open the thread, hit reply, click the paperclip, pick the 2 MB PDF, type a sentence, and send. The composer shows you 1 of 5 files as you go, so you always know how much room is left. Dragging the PDF from your desktop onto the conversation does exactly the same thing — a drop zone appears the second you start dragging.
WarmySender is a 4-pillar outreach platform — Cold Emailing, Email Warmup, LinkedIn Outreach, and Multichannel sequences. Every reply those four generate lands in one place: your Unified Inbox. That is exactly where attachments belong — the moment someone writes back and asks for the deck, you are already in a real conversation, and sending them a file is the natural next move.
Replies yes, campaigns no — and why that is on purpose
This is the one thing to take away. You can attach files to a reply you send from your inbox. You cannot attach files to a campaign or cold outreach email, and we are not going to add it, because it would cost you far more than it gives you.
| Where you are sending from | Attachments | Why |
|---|---|---|
| Inbox reply | Supported | Someone wrote to you first. Your address is already in their thread, they are expecting a file, and the trust is established. |
| Campaign or cold outreach email | Not supported, by design | A file arriving from a stranger is one of the strongest spam signals Gmail and Outlook look at — and it damages the reputation of every message from that mailbox, not just the one carrying the file. |
What to do instead in a campaign: put the material somewhere you control — your own site, a shared document, a simple landing page — and link to it. The recipient still gets what you wanted to send them, your reply rate does not take the hit, and you can update the file after the email has gone out. For how to build the sequence around that, see setting up campaign sequences, delays and conditions.
The trust math between the two cases really is that different. A cold email with a file attached asks a stranger to open something from an address they have never seen. A reply with a file attached answers a question the person just asked you. Filters read those two situations completely differently — and so does the person on the other end. More on how the filters make those calls in the deliverability FAQ.
How to attach a file
The path is Inbox → open the conversation → Reply → paperclip or drag.
- Open Inbox from the left sidebar and click the conversation you want to answer.
- Start your reply, then either click the paperclip icon in the reply box and pick your files, or drag them from your desktop onto the conversation. A drop zone appears as soon as you begin dragging, so you can see exactly where to let go.
- Check the running count and size under the composer — it reads like 2 of 5 files — so you always know your remaining headroom before you commit.
- Grabbed the wrong version? Remove any file from the list before sending and add the right one. Nothing is final until you hit send.
- Send. Your reply goes out with the files attached, exactly like any other email you would send from that mailbox.
Drag and drop is not email-only. It now works in your LinkedIn and Instagram inboxes too, so the same muscle memory carries across every conversation you handle in WarmySender.
The limits, in plain numbers
| Limit | Value | What it means in practice |
|---|---|---|
| Files per reply | 5 | Add them all at once or one at a time — the composer keeps count. |
| Size per file | 10 MB | Plenty for a pricing sheet, a proposal, a deck, or a screenshot. |
| Total per reply | About 11 MB | The combined ceiling across everything attached to one reply. |
Why the total is not simply 5 x 10 MB
Email cannot carry a file the way your hard drive stores it. It has to repackage each file so it can travel inside a message, and that repackaging makes everything noticeably bigger in transit. The ceiling is set on the packaged size, which works out to roughly 11 MB of actual files.
That gap is deliberate headroom, not a rounding error. It keeps every reply comfortably under what mainstream inbox providers accept, so your message lands in the recipient's inbox instead of bouncing back hours later with a size complaint.
Which files you can send
The allowed list covers what people actually ask for mid-conversation. Everything else is turned away for one reason: so your reply keeps landing.
Allowed
- PDF — pricing sheets, proposals, one-pagers, case studies.
- Word — contracts, briefs, anything written up as a document.
- Excel — quotes, pricing tables, data the buyer asked to see.
- PowerPoint — decks and short walkthroughs.
- Plain text and Markdown — notes, specs, quick write-ups.
- CSV — simple exports and lists.
- Images — JPEG, PNG, GIF and WebP, for screenshots and photos.
Blocked for safety
- Programs and installers — anything that runs on the recipient's machine when opened.
- Macro-enabled Office files — Office documents that carry code alongside the content.
- Archives — bundles such as zip, rar and 7z, including ones you make yourself.
- Web and script files — files whose whole purpose is to execute instructions.
These four families are the file types attackers reach for when they want to carry malware, so inbox providers and corporate mail filters routinely strip or block any message carrying them. Turning them away here is not us being strict for the sake of it — it is what makes sure your reply actually arrives.
Worth knowing: the check looks at what a file genuinely is, not just the letters after the dot. Renaming a blocked file to .pdf will not sneak it through, because that is precisely the trick the filters are watching for.
Do not try to zip it. Archives are on the blocked list too, so bundling a file up is not a workaround. If your file is too big or falls into a blocked family, share it as a link — your own site or a cloud drive — or send it in a follow-up reply.
Where to find a file you have already sent
Files you attach are delivered to your recipient exactly like any other email attachment, and a copy lands in your own Sent folder in your mailbox — so you always have the record of what went out. Re-downloading a file you already sent from inside the WarmySender thread view is not available yet, so when you need the original file back, open that message in your Sent folder and take it from there.
When a link beats an attachment — even in a reply
Attaching is the friendlier move most of the time. Here are the situations where a link is simply the more reliable choice:
- The file is over the ceiling. A 40 MB video walkthrough or a high-resolution design file is not going to fit, and no amount of bundling will change that. Upload it once, send the link, done.
- The recipient sits behind a strict filter. Banks, hospitals, government bodies and large enterprises often quarantine or strip attachments arriving from outside the company, however harmless. If your contact works somewhere like that, a link gets read where an attachment might never reach them.
- Bonus reason: a link stays current. Fix a typo in the pricing sheet after you have sent it and everyone who clicks still sees the right version — something an attachment can never do.
Frequently asked questions
Can I attach files to my campaign or cold outreach emails?
No, and that is deliberate. Attachments work on replies you send from your Unified Inbox, not on campaign or cold outreach emails. An attachment arriving from a sender the recipient has never exchanged mail with is one of the strongest spam signals Gmail and Outlook weigh, so allowing it would drag your whole campaign toward the spam folder — including the messages that had nothing attached. The alternative works just as well: put the material somewhere you control, such as your own site, a shared document, or a simple landing page, and link to it in the email. Your deliverability stays intact, the recipient still gets the file, and you can update it after you have sent.
How many files can I attach to a reply, and how big can they be?
Up to 5 files on a single reply, each up to 10 MB, with roughly 11 MB of files in total across the whole reply. The total is smaller than 5 x 10 MB because email has to repackage files so they can travel inside a message, and that repackaging makes them noticeably bigger in transit. The ceiling is set on the packaged size, which works out to about 11 MB of actual files. That headroom is deliberate: it keeps your reply comfortably under what mainstream inbox providers accept, so it lands instead of bouncing back. The composer shows a running count and size as you add files, so you always know how much room is left.
Which file types can I send as an attachment?
PDF, Word, Excel, PowerPoint, plain text, Markdown and CSV files, plus images in JPEG, PNG, GIF and WebP. That covers what people actually ask for in a live conversation — a pricing sheet, a proposal, a case study, a spec, a screenshot of the thing you are describing. If what you want to send is not on that list, share it as a link rather than looking for a way around the limit.
Why was my file blocked?
Blocked files fall into four families: programs and installers, macro-enabled Office files, archives such as zip, rar and 7z, and web or script files. These are the file types attackers use to carry malware, so inbox providers and corporate mail filters routinely strip or block any message carrying them — turning them away here is what makes sure your reply actually arrives. Renaming will not get around it either: the check looks at what a file genuinely is, not just the letters after the dot, so a blocked file renamed to .pdf is still recognised for what it is. If your file falls in one of those families, share it as a link from your own site or a cloud drive, or send it in a different format. Bundling it into an archive is not a workaround, because archives are blocked too.
How do I actually attach a file — paperclip or drag and drop?
Either, whichever is quicker for you. Click the paperclip in the reply box and pick your files, or drag them straight from your desktop onto the conversation — a drop zone appears the moment you start dragging, so you can see exactly where to let go. However you add them, the composer lists what is attached with a running count and size, like 2 of 5 files, and you can remove anything before you hit send. Drag and drop now works in your LinkedIn and Instagram inboxes as well.
Where do I find a file I already sent?
In your own mailbox's Sent folder. Every file you attach is delivered to your recipient exactly like any other email attachment, and the copy that lands in your Sent folder is your permanent record of what went out. Re-downloading a file you already sent from inside the WarmySender thread view is not available yet, so when you need the original back, open that message in your Sent folder and take it from there.
Related reading
- Campaign sequences, delays and conditions — build the follow-up that links to your file instead of attaching it
- Deliverability FAQ — what the inbox providers actually look at before they let you in
- The unsubscribe link in campaign emails — another small requirement that quietly protects every send
- Full documentation — Cold Emailing, Email Warmup, LinkedIn Outreach, and Multichannel guides
Still have questions? Email [email protected] — we respond within 24 hours on business days.