[2.0.3.1] - Email regex doesn't seem right

The email regex in Opencart is the following:
I think the 2nd dot is unescaped, unless the purpose of this regex is to make sure, that the last 2-15 characters doesn't contain anything else, but letters of the English alphabet. Can someone confirm this?

I know it's not a major issue at all, it's just something I came across when I was making a vqmod for the returns system.