Sorry, I don’t think we can understand what you’re asking until you give us more information. Performance in what — your mail server? What is the architecture in your system. By ’400′ do you mean an AS400? What part does your mail server play in this issue and what kind of mail server? Is the rest of your architecture Windows, or…? Where does storage come into the picture?
First place to look would be for any indexes over the file. What fields are indexed? Simply adding records to the file won’t be a problem, but reindexing might be. And journaling shouldn’t be a problem, though I’d wonder why journaling was being done for this kind of file.
Actually, I’d wonder why a database file has e-mails in it in the first place, but it’s your choice.
I’d also wonder what the “2 million records” means. Is that representative of 2 million different e-mails? Or do individual e-mails result in multiple records. If they’re all one e-mail per record, that’s an awful lot of e-mail.