Why is my Gmail forward node not recognizing the binary attachment?

It seems that while the Gmail trigger is correctly downloading your attachment (stored in a binary field named data_0), the merge node isn’t preserving that binary data so that the subsequent Send Message node can use it. Here are some points and suggestions to help troubleshoot and resolve the issue:

Possible Causes

• Merge Configuration:
  The merge node might be configured such that it only merges JSON data or that it overrides (or “drops”) binary data when combining the inputs. If the merge block doesn’t correctly merge the binary fields from the Gmail trigger with what’s expected by the Send Message node, the binary field (data_0) ends up missing.

• Data Alignment:
  For binary data to persist when merging, the items (and their indexes) should align. This means the binary field from the Gmail trigger must match the corresponding item from the merge block. A misalignment can lead to the binary file not being carried over.

Potential Solutions

1. Check the Merge Node Settings:
   In your merge node, review the mode you’ve chosen (e.g., “Keep Key Matches,” “Merge By Index,” etc.). Ensure that the setting preserves all binary fields. Some merge modes may only merge JSON properties by default while ignoring or overwriting binary data. If available, use a mode that appends or retains binary data from all inputs.

2. Verify Binary Keys:
   Double-check that after the merge, the item still has a binary property named exactly data_0. If the merge operation renames or removes binary properties, the Send Message node won’t find the attachment. You might insert a set node or a function node between the merge and the Send Message node to inspect the item structure and confirm the existence of data_0.

3. Adjust Workflow Structure:
   If merging is used purely to combine context or data but not to modify binary fields, consider bypassing the merge for binary data. You might split the workflow so that the Send Message node always receives the binary data directly from the Gmail trigger and then use additional nodes for merging the non-binary parts as needed.

By ensuring that the merge node’s configuration is tailored to retain binary data intact, the Send Message node should then correctly pick up the expected attachment from data_0.

Give these adjustments a try and check the item’s structure after the merge to help pinpoint where the binary data might be getting dropped.