I remember AP Stylebook made it “email” in 2011, while Chicago held onto “e-mail” until the 17th edition in 2017 — does that timeline match your references? I’m double-checking a house style note before I fix two dozen instances in a 2013 manual.
AP 2011 is right, and you can add that The New York Times dropped the hyphen in 2013 (“Goodbye to ‘E-Mail’”: https://publiceditor.blogs.nytimes.com/2013/10/23/goodbye-to-e-mail/), while Chicago didn’t switch until the 17th. For that 2013 manual, run a targeted find/replace like \be-?mail(s|ing)?\b so you catch plurals and gerunds without mangling addresses — let the hyphen rest in peace. Small caveat: if the manual follows Chicago 16, you could leave hyphens for period fidelity.
Looks right to me: AP went sans hyphen in 2011 and Chicago followed in the 17th (2017). My go-to cleanup step on a 2013 guide is a regex pass — \b[Ee]-mail(s|ed|ing)?\b — so ‘e-mail’ and its variants flip cleanly, then I spot-check compounds like ‘e-mail-based’ that a simple replace misses. Any UI labels or legacy product names where you still need the hyphen?
Your dates line up: AP dropped the hyphen in 2011, and Chicago waited until the ‘17th edition’ (2017). Do you also need to adjust any index entries or PDF bookmarks? I’ve found ‘e‑mail’ tends to survive there even after a global replace.
@sophia_johnson44’s regex is solid — also sweep for the nonbreaking‑hyphen version “e‑mail” and line‑broken “e-↵mail”; those hyphens love to hide in PDFs. Timeline checks out, but caveat: if your house keeps “e‑commerce” or “e‑book,” don’t unhyphenate those — should those stay as-is?