Don't attach anything to the first email unless the person has already asked for a file or works somewhere that requires one. Put the useful part in the body of the email, offer to send the rest, and attach it in your reply once they say yes. A file on a first message from someone they've never heard of looks, to both a person and a mail filter, like the opening of an invoice scam.
There are real exceptions, and they matter to some senders more than others. This guide sorts the four ways to handle a file, shows when each fits, and gives you the wording for the most common moment: the reply that says "send me the deck."
Why a file on the first email costs you
Two readers see your email before the buyer does. The first is the mail system. Many company mail gateways open attachments in a sandbox before delivering the message, which can delay it or quarantine it. Filters also learn that mail with a file from an unknown sender is a common pattern for phishing, so the file raises the odds of a spam-folder landing. Nobody publishes the exact weighting, and it varies by provider, but the direction is consistent.
The second reader is the person. Opening an attachment from a stranger is something IT departments tell staff not to do. Even if your PDF is harmless, you are asking for trust you haven't earned yet. A line of text costs them nothing to read. A file costs them a decision. For the wider picture on what pushes mail toward spam, see our deliverability basics and the SPF, DKIM and DMARC setup guide.
Four ways to handle a file
| Option | Filter risk | Reader effort | Best for |
|---|---|---|---|
| Say it in the email | Lowest | None | Most first emails |
| Offer to send it | Lowest | One word to reply | Samples, price lists, one-pagers |
| One link to your own page | Low | One click | Portfolios, case studies |
| Attach a PDF | Highest | Open and read | Requested files, formal buyers |
Start at the top and move down only when the row above doesn't do the job. "Say it in the email" beats the others more often than people expect: if the content of your PDF is a price range, a service list and two customer names, those are three sentences.
The cases where an attachment is right
Three situations justify it. A procurement or purchasing office that collects capability statements, insurance certificates or vendor forms in PDF, because the document is the thing they need on file. A recruiter or hiring manager who asked for a resume. And anyone who has said "send it over." In these cases the file isn't a pitch. It's the paperwork.
Tessa runs Northgate Refrigeration Service, which repairs walk-in coolers and freezers. She wants school district food-service offices as customers, and they buy through purchasing departments that ask for a license number and an insurance certificate. Her first email carries no file:
Hello Mr. Okafor, I repair walk-in coolers and freezers for school kitchens in the county, with same-day response when a unit goes down. I have a one-page capabilities sheet with our license and insurance details for your vendor file. Shall I send it here, or does it need to go through your vendor portal?
The last question is the useful one. Some purchasing offices accept email, some require a portal upload, and some do neither until a department requests you. Asking costs a line and tells you the process. When he says "email is fine," she attaches the PDF in her reply, in the same thread, where nobody is surprised by it.
File size, type and name
When you do attach, a few rules keep it from becoming the problem:
- PDF only. No Word, PowerPoint, Excel or zip files. Those formats can carry macros, and filters treat them with more suspicion.
- Under 1 MB if you can. Gmail's published attachment limit is 25 MB, but that's a ceiling for friendly mail, not a target. Compress the images.
- Name it for the reader: Northgate-Refrigeration-Capabilities.pdf, not final_v3_REAL.pdf.
- One file. Two attachments look like a package.
- No images in your signature. Many mail clients count an inline logo as an attachment.
If the file is bigger or changes often, host it on your own site or in cloud storage set to "anyone with the link can view," and send one plain link. Check the link in a private browser window before you send.
What to send after they say yes
Reply in the same thread, attach the single file, and keep the cover note to three lines: what it is, the one thing to look at first, and what you'd like them to do next. Example: "Attached is our one-page sheet. Page one has the license and insurance numbers your office asks for. If anything is missing from your vendor file, tell me and I'll fix it today."
Which option to use, by situation
- Selling a service to an owner you found yourself: say it in the email, offer a sample.
- Selling creative work: one link to a page with three examples, nothing attached.
- Writing to a purchasing office, school district or agency: no file on the first email, ask how they take documents, then attach the PDF in your reply.
- Applying for a job or a contract someone posted: attach what the posting asks for, and nothing more.
- Replying to someone who asked for a file: attach it. The request is the permission.
A reply to "send me the deck"
This reply is polite, noncommittal and sometimes a way of ending the conversation. Don't just fire a 30-slide file back. Send something shorter that moves it forward:
Happy to. The full deck is built for a walkthrough and reads thin on its own, so here is a one-page summary instead: [link or attached PDF]. If you tell me which of the three things on page one matters most to you, I'll send the section on that, or we can cover it in ten minutes on Thursday.
The longer treatment of this moment, including what it means when the answer is a brush-off, is in how to respond when a prospect says "send me more info." To see how attachments fit with bounces and delivery trouble, read cold email bounce rate, and for how plain formatting compares with a designed email, HTML versus plain text for cold email is the companion to this one. A file is one of several common cold email mistakes worth catching before a send.
Sorting out which contacts want a file and which want a portal link is the kind of detail that gets lost by hand. Rocketship finds the buyers, emails them from your own Gmail, follows up, and books the meeting on its own. Plans that get you customers start at $24.99 a month (Launch), and every monthly plan starts with a 7-day free trial, card required. See how the AI workers run outreach.