searching for partial email address returns eratic results

When searching in Advance Search for a partial email, some partial forms are not matched, while other partial forms of the same address are matched.

Example:
1. Create a contact with email address 1_0bf0d07@example.com
2. Visit civicrm/contact/search/advanced?reset=1
3. Enter 1_0bf0d0 under "Complete or partial email address", and search; one result is found.
4. Adjust search criteria to enter 0bf0d0 in the same field, and search; no results are found.

It appears that the partial email search is matching from the start of the string only, not anywhere within the string.