How quickly should a reliable agency reply to emails?

A professional travel agency ought to answer those first enquiries, and any email back-and-forth, within 24 hours, while remembering the global time zones, of course. If delays keep showing up, like a few days at a time, it often points to understaffing, and then you can expect messy communication while you are on your holiday.

During the active part of itinerary planning, quick communication that is both clear and direct is one of the best signals of operational capability. If a tour operator moves slowly when they are trying to secure your booking, their reaction speed during a mid-trip crisis is likely to be even poorer.