I use a VPS but with Tradestation I don't send the email alert from platform to gmail.
Why? I must open port? I use smtp.gmail.com and SSL with port 465

tradingest,

it's hard to tell without an error message or further information.
You can check here if your configurations match:
https://community.tradestation.com/Discussions/Topic.aspx?Topic_ID=142769

This might apply as well as in this issue is with Gmail:

Sending alerts by email from MultiCharts (Gmail) I recently ran into the same problem with gmail. Google blocks any attempts to sign into your account from any software that is not gmail. To prevent such blocks, you have to go through the 2 step authentication process on google. Once thats done, you …

Regards,

ABCTG