Does Email with Starter Cloud allow it to come from my email/domain?

I don't think so. If you look at the pricing page it says:

Custom SMTP server

is at the enterprise level. Which makes sense since they don't even provide email support at the starter level.

I don't use email, but according to the sendEmail() page it says:

You can use the replyTo parameter to set a specific email address for recipients to respond to when they use the reply option in their email program. Ensure that the email address provided in replyTo is valid.

On a side note, love how you call the MacOS app, the "OnPrem" version.

Hello,

Moving from the Mac OnPrem version to the Starter Cloud version allows you to use email functionalities with your own domain. Starter Cloud supports configuring email so that messages can appear to come from your domain (e.g., admin@acme.com). This maintains your branding and facilitates effective communication through the Starter Cloud platform.

@Matthew

yep works fine (but in any case you can elect for a free trial to try out)

Test Example

Contact selection on a form

Processing page (note CEmail formula to confirm contact email actually exists

then click the Order confirmation button to send

email in clients inbox (in this case test to myself ) 

above letter is fed frm a template form

Script behind the order confirmation button

if not CEmail then
    alert("No valid contact in email field")
else
    let myName := "Order Confirmation.pdf";
    let thisBody := first((select JobBag_Settings).OrderConfirmationLetter);
    let myEmail := userEmail();
    let log1 := first(select Quote_Settings).HTMLxLogo;
    let log1 := replace(log1, "{UL1}", shareFile(first(select Quote_Settings).xLogo));
    thisBody := replace(thisBody, "{Ord Company}", text('Ordered By'));
    thisBody := replace(thisBody, "{Job Bag}", text('Job Bag'));
    thisBody := replace(thisBody, "{Order Date}", text('Order Date'));
    thisBody := replace(thisBody, "{Order Name}", text(EContact));
    thisBody := replace(thisBody, "{Order Ref}", 'Order Ref');
    thisBody := replace(thisBody, "{Qty}", text(Qty));
    thisBody := replace(thisBody, "{Desc}", Desc);
    thisBody := replace(thisBody, "{Total Sell}", text('Total Sell'));
    thisBody := replace(thisBody, "{Comment}", text('Order Confirmation Comment'));
    thisBody := replace(thisBody, "{Del Company}", text('Delivery To'));
    thisBody := replace(thisBody, "{Del Address}", text('Delivery Address'));
    thisBody := replace(raw(thisBody), "{xLogo}", log1);
    AckFlag := 1;
    sendEmail({
        from: myEmail,
        to: CEmail,
        bcc: "sales@118printdesign.co.uk",
        subject: "Order Acknowledgement from 118 Printgroup",
        text: "Order Confirmation",
        html: thisBody
    });
    alert("Order Confirmation Email has been Sent")
end

NOTE - I am on prof version but when i was on the basic version all worked okay but there was a lower email usage limit - the only other thing that on ther Starter version there is a monthly limit 150 emails (3000 on prof and unlimited ion Enterprise) and i am not sure if on starter they go out instantly but a quick email to support will confirm this)