extracting the domain from an email address

Good morning,
I am searching for a better more efficient way to extract the domain
portion of an email address. The two I have been using are very expensive.
The one extract I mostly use: substring(email from '@(.*)$')
also has an index on the email column which is the full email
address:
btree (email DESC) WHERE email::text =
"substring"(email::text, '@(.*)$'::text) AND length(email::text) > 0,
The other extract:
substr(e.email,(strpos(e.email, '@') + 1))
Currently has no index.

The referenced table has 72 million rows. The email column can be empty
(ergo the length = 0 check. I am running postgresql 9.4.

Any insights/observations welcome.

--
*Mark Steben*
Database Administrator
@utoRevenue <http://www.autorevenue.com/> | Autobase
<http://www.autobase.net/>
CRM division of Dominion Dealer Solutions
95D Ashley Ave.
West Springfield, MA 01089
t: 413.327-3045
f: 413.383-9567

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