I followed the "setting up SMTP Archiving" doc from the 11.0.1 documentation - https://www.veritas.com/support/en_US/article.DOC7414 - starting on pg 24 but the short version on the EV side is:
1. create SMTP archive
2. set up SMTP archiving policy / retention categories
3. configure SMTP server settings for all servers in the site (rt click SMTP in the Targets section and choose properties) (wish it was under the site properties)
4. add the target address (also under Targets > SMTP), which will be the mail contact email address you create in Exchange (below)
5. create the SMTP task and config the holding folder
(many of these can be set up via the wizard)
For Exchange (2010 or 2013), you need to do 3 things:
1. Create a mail contact in Exchange - i.e. SMTPJournal@ev.yourcompany.com
2. Create a Send Connector in Exchange - i.e. "SMTPArchiving" or "EV" and configure so Exchange sends anything destined to ev.yourcompany.com to a smart host and set the IP of the EV server as the smart host. Make sure NOT to include subdomains. Note: You can do DNS if you want but it's more work. If you want to set up a secondary EV server for SMTP archiving, just add it in the smart host list. DNS can be handy if you want to set MX preferences for your ev.yourcompany.com DNS domain and weight them differently.
3. Set the global journal rule to send a copy to your mail contact you created - i.e. SMTPJournal@ev.yourcompany.com
Besides the SMTP Archiving doc, here's a good white paper here if you haven't seen: https://www.veritas.com/support/en_US/article.DOC7982
Regarding stress testing - all the companies I have implemented for have been relatively small ( < 5k users) so I can't give you any real numbers except to say we haven't seen any backlog. The white paper mentioned also says 120k msgs per hour.
Hope this helps!