Gmail allows you to define multiple “send as” addresses. So if you want to use your GMail account but send email from You@YourCustomDomain.com, this can be supported. But, to support this you need to have a server set up that will relay the SMTP mail for you. For security reasons Google won’t allow you to relay non GMail addresses from their servers (unless you subscribe as a Google Apps user with a custom domain name – which isn’t free).
So, to get around this I decided to use my existing Windows cloud server and the Microsoft IIS SMTP service. First, make sure SMTP is installed on the server as I already blogged about in the past. That post was written for Windows Server 2008 but the steps are basically the same for Windows Server 2012. After installing the IIS SMTP service you need to configure it for relay, which I also already blogged about.
Notice in that second post that the checkbox for “Allow all computers which successfully authenticate, regardless of the list above”. That is key. So that list only allows relaying from the local server (127.0.0.1). To successfully authenticate you need to create a user account on the server. I suggest giving it an obscure name (yes, security by obscurity) and a super-super-super strong password. The last thing you want is for a spammer to get access to your SMTP service.
Once that new user account is set up you should be able to use that username/password combination to authenticate for SMTP relay. When entering this information in GMail you’ll need to select the less-secure plain text authentication option (or configure a certificate on the server, which is well beyond this post).
Give it a try – it works great.