Yes, attachments are capped at 10MB total per email, but the real limit you're likely hitting is your SMTP provider's own cap, not ours — Gmail caps outgoing attachments around 25MB but a lot of transactional SMTP providers cap much lower, and corporate mail relays are often set as low as 5–10MB. Since it's failing around 8MB specifically, that smells like your SMTP provider's limit rather than ours. For anything sizable, we'd actually recommend linking to a hosted file (Google Drive, Dropbox, etc.) instead of attaching directly — it also tends to help deliverability, since large attachments are themselves a spam signal to some filters.