What does “custom domain” mean for this service? I tried searching for the same question from others, your responses were... let's say, consistently unhelpful. Can you finally clarify what it actually does, especially for email sending?

Second, looking at Tier 1 plan and 2: If emails are synced and replies are sent via your platform, will the recipient see my actual email address (e.g., shala@center.com), or does it come from your domain? And is that why a custom domain is needed?

Thanks, looking forward to a clear answer this time.