That's a real limit worth understanding — unlike the simpler case in the earlier SPF thread, SPF has a hard cap of 10 DNS lookups total across the whole record (each include: can itself trigger more lookups internally, they add up fast). This usually happens when a domain already sends through several services (e.g. Google Workspace, a CRM, and now SubsiMail) and each adds its own include. Can you paste your current full SPF TXT record here? I can help figure out which includes are actually still needed and flatten or trim the rest.