David, The configuration sample shipped with stunnel  includes a section designed to send smtp mail via GMAIL. Something like this: [gmail-smtp]client = yesaccept = 127.0.0.1:25connect = smtp.gmail.com:465verifyChain = yesCAfile = ca-certs.pemcheckHost = smtp.gmail.comOCSPaia = yesprotocol = smtpprotocolUsername=yourmail@gmail.comprotocolUsername=youpassword

However, recent security changes on GSuite may impact this. Google is enforcing the Oen Authentication protocol (OAuth) . Check this: https://www.bleepingcomputer.com/news/security/google-to-force-oauth-in-g-su... I think you can still make it work if you follow the instructions published here: https://support.google.com/a/answer/176600?hl=en#zippy=%2Cuse-the-gmail-smtp...

On Office365, the situation is similar. Microsoft has been disabling legacy protocols, but you may be able to achieve what you want following this guide: https://docs.microsoft.com/en-us/exchange/mail-flow-best-practices/how-to-se...

Now, If this helps you, feel free to send me some money at my Paypal :)   regards,Jose On Saturday, April 24, 2021, 03:50:54 AM GMT-5, David Rose (dsr) dsr@navigator.co.uk wrote:

I need an Stunnel config that will allow my Windows app that only can send SMTP without any authentication or encryption to be able to send email via Gmail or Office 365.

Is this something that someone would be able to write for me and if so, what would you charge ?

Thanks

David