If a file you attach to a reply isn't reaching your recipient — even a small one — this is a known limitation with how certain mailbox setups handle attachments today, not something wrong with your account.
Why this happens
Not all mailbox setups currently support sending file attachments directly. Mailboxes that are connected individually (rather than pulled automatically into your sequencer) don't pass attachments through when you send — the file gets stripped out even if the email itself goes through fine.
The best workaround
Instead of attaching the file directly, share a link to it (Google Drive, Dropbox, or similar) in the body of your email.
If you're using a Global Custom Tracking Domain, links sent through it will match your sending domain — which can actually help deliverability compared to a raw attachment.
Is this being fixed?
We've logged this with our product team as a feature request to support direct attachments across all mailbox setups. There's no fixed timeline yet — if this is affecting you, contact us and we'll keep you posted as it develops.