This endpoint lets you look up a warm‑up campaign by the mailbox’s email address instead of its numeric campaignId. It is ideal when:

You only know the sender’s email (for example, when a user re‑opens your settings panel) and need to retrieve the associated campaign details quickly.

You want to check whether a mailbox is already connected before attempting to create a duplicate campaign.

You need the campaignId so that subsequent calls—such as starting or pausing warm‑up—can target the correct record.