What do you mean ?

So you want to use two SMTP accounts?

It’s nice in theory but bad on implantation.
This kind of thing will require dozens of custom integrations to any kind of contact or forms plugins or e-commerce plugin or anything that require SMTP.

If I understand you right, you want to be able to send emails from two different addresses on the same domain. Something along the lines of:

[email protected] and [email protected]

You don’t actually need to log into two different SMTP accounts to do the above.
You could for example create [email protected] and use that to send ALL of your emails.
But in the Reply To: field, you set [email protected] and [email protected]

When the email is validated at the receivers end, it’s done using the @yourDomain.com part and not by the actual address.

So long as the domains match in the From: (smtp@) and ReplyTo: (sales@ or general@) then you won’t fall foul of any anti-spam measures.

What I think Yehudah was thinking that you wanted to do was have the ability to log into [email protected] and [email protected] which he is right, would need a heck of a lot of customisation to achieve.

So long as the different addresses you want to use are on the same domain (as you stated in your original post), then doing as I suggest will work. (I do it all the time).