Efficient searching for email addresses?

Although AppSearch matches email-addresses quite well, it is too eager at returning documents where only the domain matches.

For instance, when searching for helpme@gmail.com, it might also return thousands of documents with "gmail" in the address.

Perhaps creating an additional field with only the first part of the address would help, but the domain is still important for the search nonetheless. Also, adding more fields has performance impact.

What would be a good and efficient way of searching for email-addresses?

@Iconeer I would try indexing email into multiple fields, as you suggest. You could then boost (or negative boost) the two fields separately, depending on the type of relevance you are looking for.

I wouldn't expect adding an additional field or two to have much impact on performance.