6. The method of claim 1 wherein retrieving the matching domain correction record comprises using a key to lookup, in constant time, the matching domain correction record in a key-value store, wherein the key is based on the misspelled domain name of the unprocessed email address.
1. A method comprising: durably storing a plurality of domain correction records, wherein each domain correction record of the plurality of domain correction records comprises a misspelled domain name and one or more candidate domain name corrections; detecting that an unprocessed email address of an attempt to log in to an online user account is not contained in a plurality of known email addresses, wherein the unprocessed email address comprises a misspelled domain name, wherein each known email address of the plurality of known email addresses comprises a domain name; retrieving, based on the misspelled domain name of the unprocessed email address, from the plurality of domain correction records, a matching domain correction record having a same misspelled domain name as the unprocessed email address; causing the one or more candidate domain name corrections of the matching domain correction record to be displayed on a client device; wherein each of the one or more candidate domain name corrections of the matching domain correction record occurs within the plurality of known email addresses at a frequency that exceeds a threshold; wherein the method is performed by one or more computers.