The emails you send after the initial signup are completely missing the "Date:" header, and so end up sorted as the last items in my inbox.
Should be all fixed up now.
It should be added now and processed on all future mailings.
Please see https://digitalocean.uservoice.com/forums/136585-digital-ocean/suggestions/3551213-fix-mail-headers-on-signup-credit-granted-etc-t
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