Email works well for a small approval that has one clear decision-maker and little follow-up. It becomes harder to operate when recipients change, attachments are revised or several approvals must occur in order.
What email preserves
An email thread preserves messages and attachments. It does not necessarily identify the authoritative document version or distinguish a comment from a final approval. A request copied to several people can also leave responsibility ambiguous.
For a simple process, put the requested decision, responsible person and document version in the message. Record where the final decision will be kept.
What a task system must add
A task system earns its place by making pending work and its responsible role visible. It should distinguish approval, rejection and a request for changes. Test whether the decision remains attached to the version that was reviewed.
A generic “done” checkbox may not carry enough meaning. Define whether completion means that someone responded or that the requested decision was accepted.
Test absence and revision
Use two examples in a tool evaluation: the approver is unavailable, and the submitted document changes during review. Check who receives the reassigned work and whether the earlier approval remains applicable.
Choose a system when these cases recur and cannot be followed reliably in email. For selecting between a purchased system and a custom implementation, see buy vs build for approval workflows.