WHD setup instructions recommend an inbound and outbound email address for Web Help Desk. Is this absolutely necessary or can we get away with just one email address for both inbound and outbound email?
No you should be able to just use one. 90% of the customers that support helps have a single email address.
We use one.
That's what you get for reading the documentation!
I emailed Solarwinds tech support and they said we can get away with one as well, but the pre-sales engineer I spoke to recommended two addresses, one inbound and one outbound, because of a potential loopback issue in case users reply to the single email address improperly? When would that be the case. If a new ticket is issued, for example, through the email address support@mycompany.com and a user responds to the same email address (with the reply button) as it was used as the outbound ticket, as well as the inbound ticket, would there be an issue, or should they use the Add Note to ticket feature which is a link within the email to update the ticket, but that just creates another email to the same (inbound and outbound) email address, if you're using the same address.
We've never had that issue garciann - people reply to the initial ticket email all the time and it just adds a note to the ticket. I honestly doubt any of our users use the "add note" link.