Alternative way to send email without getting "Suspicious sign in prevented"

Alternative way to send email without getting "Suspicious sign in prevented"

Is there any free way to send email from an app, without getting
"Suspicious sign in prevented"?
Currently, I'm creating a dummy GMail account, to send email from my app
using the following described way :
http://stackoverflow.com/a/3649148/72437
However, once in a while, due to heavy usage by my app users from
different location, certain message will fail to send. I get the following
message from Google :
Hi xxx,
Someone recently tried to use an application to sign in to your Google
Account - xxx@gmail.com.
We prevented the sign-in attempt in case this was a hijacker trying to
access your account. Please review the details of the sign-in attempt:
Is there any alternative way I can try out, so that I can always send
email successfully from my app?