The Mail app

Manage → Apps carries a Mail card on the Built-in shelf — it needs no installing like a marketplace app; opening it takes you straight to its configuration under Manage → Settings → Mail.

What it does

System emails sent to your shoppers — account verification codes, password-reset codes — go through the platform's shared mail server by default. Fill in your own SMTP here and they go through your server instead: recipients see your domain as the sender, and your sending reputation is your own.

With nothing configured, everything still works — the platform sends on your behalf. This is an optional upgrade, not a required step.

Configuring it

Host, port, username, password, sender name and address — from your email provider.

• The password is write-only. Once saved, the field only says "saved" — nobody can read the value back, you included. It is encrypted before it touches disk. Type over it to change it; leave the field empty on save to keep it.
• Send test fires a real email to an address you choose and reports the result immediately — an SMTP failure shows its actual message, not a generic "something went wrong".
• Remove the configuration and the site returns to the platform's server.