gistfile1.sql

WITH emails AS (
    SELECT e.id, split_part(e.email, '@', 1) || row_number() OVER (PARTITION BY split_part(e.email, '@', 1)) AS email
    FROM email_addresses e
    WHERE e.email !~ '@(domain|example).com$' AND e.email <> ''
)
UPDATE email_addresses e
SET email = emails.email || '@example.com'
FROM emails
WHERE e.id = emails.id;