Skip to main content
The Attachment node fetches the actual file bytes of an email attachment when the workflow reaches it. A Mailhook trigger gives downstream nodes only attachment metadata (id, filename, content type), so the trigger input stays small. The Attachment node downloads the bytes for the attachments you actually need, then hands them to the next node as base64 content.
The Attachment node only works in a workflow started by a Mailhook trigger. It reads the triggering email from {{ input }}, so the designer will refuse to save a workflow that has an Attachment node without a Mailhook trigger.

​
When to use it

  • “When an invoice arrives by email, pull the PDF and file it in the knowledge base.”
  • “Forward every image attachment on to a colleague.”
  • “Grab the one spreadsheet on the email and run it through a transform.”
You only pay the download cost for attachments a workflow consumes, so it is fine to receive large emails and fetch nothing.

​
Configuration

FieldDescriptionTemplated
LabelDisplay name on the canvasNo
ModeSingle returns the first matching attachment as an object; Multiple returns every match as a listNo
Content typeFilter by MIME type. Comma-separated, wildcards allowed, e.g. application/pdf, image/*No
Filename patternFilter by filename glob, e.g. *.pdf or invoice-*.csvNo
Attachment IDSelect one exact attachment by id. When set, the other filters are ignoredYes
Min / Max sizeFilter by declared size in bytesNo
Fail if no attachment matchesOff by default: the step produces no output and the run continues. On: the step failsNo
Email ID (Advanced)Defaults to the triggering email. Leave blankYes

​
Filters

All filters are optional and combined with AND. Leave them all empty and choose Multiple to fetch every attachment on the email. The content-type filter accepts a comma-separated list and matches if any pattern matches, so application/pdf, image/png matches either, and image/* matches any image.

​
Output

In Single mode the output is one object: 
{
  "filename": "INV-2041.pdf",
  "contentType": "application/pdf",
  "size": 48213,
  "content": "JVBERi0xLjQK..."
}
content is the file bytes, base64-encoded. In Multiple mode the output is a list: 
{
  "attachments": [
    { "filename": "INV-2041.pdf", "contentType": "application/pdf", "size": 48213, "content": "JVBERi0xLjQK..." }
  ],
  "count": 1,
  "totalBytes": 48213
}
If nothing matches, Single mode outputs nothing (use a Condition node to branch on it) and Multiple mode outputs count: 0, unless Fail if no attachment matches is on.

​
Using the bytes downstream

The output is shaped to drop straight into the nodes that consume files. With an output variable of attachment:
  • Send Email attachment: set filename to {{ attachment.filename }} and content to {{ attachment.content }}.
  • Knowledge document input: set the input to {{ attachment.content }}.
In Multiple mode, put a Loop node over {{ attachment.attachments }} and reference each item’s content and filename. See Passing Data Between Nodes.

​
Limits

  • Per attachment: each file is capped (10 MB by default). A larger file fails with a clear error. Base64 inflates the size roughly 1.33 times.
  • Per run: the total downloaded across all Attachment nodes in one run is capped (25 MB by default). Exceeding it fails the run.
  • Retention: received emails are retained for 30 days. Re-running an older execution can fail to download because the attachment link has expired.