I get message "[Buildroot] ⚠️ Mailbox is full for buildroot@busybox.net" from Noreply@busybox.net contains "Dear buildroot , Your mailbox buildroot@busybox.net is almost full."... I (again) suggest move buildroot project to github.com Contributing via github.com is more easy then current email way.
sounds like you received spam. attach the full e-mail here if you feel it was legit. but we don't generally use emojis.