Alan - I use both the standard email field and the button script via sendEmail

in fact I use sendEmail scrip to issue all order acks/delivery notices etc. thus I send some 50-60 per day and all have an attachment apart from when the service has been down I had not had any instances when a client has not received them. to be fair I use ms 365 and outlook accounts and have no experience with Gmail, but you do go onto say you get your mails which kinda suggests that Ninox/sendEmail is at least doing it's job...

if it helps

this is one of my button scripts

if Status < 2 or Status > 3 then
    alert("job Status is not in production")
else
    Status := 3;
    if not 'Email+' then
        alert("No valid contact in email field")
    else
        if DispFlag = 1 then
            alert("Dispatched Confirmation already sent!")
        else
            let thisBody := first((select SystemFile).OrderDispatchedLetter);
            let myEmail := userEmail();
            let myAtt := first(files(record(SystemFile,1)));
            thisBody := replace(thisBody, "{Ord Company}", text('Ordered By'));
            thisBody := replace(thisBody, "{Order Name}", text('Order Name'));
            thisBody := replace(thisBody, "{Job Bag}", text('Job Bag'));
            thisBody := replace(thisBody, "{Order Date}", text('Order Date'));
            thisBody := replace(thisBody, "{Order Name}", 'Order Name');
            thisBody := replace(thisBody, "{Order Ref}", 'Order Ref');
            thisBody := replace(thisBody, "{Qty}", text(Qty));
            thisBody := replace(thisBody, "{Desc}", Desc);
            thisBody := replace(thisBody, "{Del Company}", text('Delivery To'));
            thisBody := replace(thisBody, "{Del Address}", text('Delivery Address'));
            DispFlag := 1;
            sendEmail({
                from: myEmail,
                to: 'Email+',
                subject: "Your order has been dispatched by 118 Printgroup",
                text: "Goods Dispatched Confirmation",
                html: thisBody,
                attachments: myAtt
            });
            alert("Goods Dispatched Email has been Sent");
            DisplayMenu := 1
        end
    end
end