Email Attachments: Replies Yes, Campaigns No
There are two answers here, and the difference matters:
- REPLIES — YES. You can attach files to a reply you send from the Unified Inbox. Click the paperclip in the reply box, or drag files straight onto the conversation. Up to 5 files, up to 10 MB each, and about 11 MB of files in total per reply. Full details: https://warmysender.com/documentation/how-do-i-attach-a-file-to-an-inbox-reply
- CAMPAIGN AND COLD OUTREACH EMAILS — NO, and that is deliberate. Attachments are not supported on campaign emails and won't be.
Why campaign emails don't take attachments:
- An attachment arriving from a sender the recipient has never exchanged mail with is one of the strongest spam signals Gmail and Outlook weigh.
- Allowing it would drag a whole campaign toward the spam folder — including the messages that had nothing attached.
- File size also slows delivery and can trip provider rate limits.
- For cold outreach specifically, recipients are wary of files from strangers, so attachments tend to hurt responses rather than help them.
What to do instead in a cold email:
- Link to a hosted file — put your PDF, brochure, or document on your own website, a shared drive, or a cloud folder, and include the link. This is the safest approach and you can update the file after sending.
- Use a landing page — a simple page with your content, linked from the email. This also shows you who visited.
- Put the key points in the body — instead of attaching a proposal or one-pager, write the two or three lines that matter directly in the email.
- Send the file once they reply — the moment a prospect writes back, you're in a conversation, and you can attach files to your reply straight from the Unified Inbox.
What you can attach to a reply: PDF, Word, Excel, PowerPoint, plain text, Markdown and CSV files, plus images (JPEG, PNG, GIF, WebP). Programs and installers, macro-enabled Office files, archives (zip, rar, 7z) and web or script files are blocked, because inbox providers and corporate filters routinely strip or block messages carrying them — so blocking them here is what makes sure your reply actually arrives. If your file is one of those, or it's over the size limit, share it as a link instead.
Best Practice: treat your first cold email as a conversation starter, not a presentation. Save the detailed materials for after you have the prospect's attention — which is exactly when reply attachments become available to you.
Note: If you want to add inline images (logos, screenshots, banners) to your campaign emails, WarmySender does support this — see the 'Images in Campaign Emails' guide for details.