Hi Margie,
The problem isn't with matching between a field called domain and the domain on the email record so much as it would be with generating the appropriate domain to populate the Account domain field with. Since there are situations where a company may have multiple domains (think big brands like IBM, I've seen them with a variety of domains over the years depending on business unit and geography of the contact) you would need to accommodate for multiple domains per account (I've seen this done via a lookup of some kind either to a data set maintained in the prospect records or even just a lookup table). But that being said you couldn't necessarily take every email address linked to an account as golden since data is never perfect, you would need to do some manual work on occasion to make sure you domain list is up to date and also doesn't contain personal email address domains (like my gmail, yahoo or hotmail examples). So in essence you're not manually updating all of your contact/lead records linkage, that would be done via the logic in Eloqua, you're only making sure you don't have inappropriately matched domains linked to accounts. The scenario being if you accidentally have my company email address @pedowtizgroup.com and my personal email address @gmailcom and now it looks like my company account The Pedowitz Group has two domains, pedowitzgroup.com and gmail.com if you just use automation to determine what domains exist at an account - if you have a scrubbed list then a person could easily say, oh yea that gmail.com domain is personal, scrub that out. Apologies if this is redundant or you guys do have exceptional data (and if you do props for that for sure!) but the reality of the data i've seen over the years as a consultant, in-house person and someone who worked for ReachForce (who does database cleanup work) is that i rarely have seen data so clean that it could be used as is without some human eyes on it.
Best,
Lauren