Tag
Fourteen production failure modes that never show up in testing: retry duplicates, late OTPs, alignment failures, the Gmail and Yahoo thresholds, bounce handling done backwards, and the it-works-in-testing trap.
DAN 
Why WooCommerce order confirmations land in spam, how to confirm the diagnosis in Gmail in one minute, and the two-part fix that ends it: a real sending service plus the DNS records that prove your domain.
DAN 
The four DNS records behind every email your product sends, explained with one mental model, real record examples, and the failure modes that put authenticated mail in spam anyway.
DAN