Hello,
In epesi we differentiate between Company e-mails and Contact e-mails. If you assign an e-mail address to company (there's a field for that in Companies), you can then write an e-mail, putting that company name in recipient. After sending, that e-mail will be archived directly under the company (if you enabled archiving that e-mail) and Company name will be used as a label for recipient.
From what I understand you'd like to send e-mails to a contact and then have the recipient field display (additionally?) the Company this contact is assigned to. Currently, this is not possible. And I'm afraid it'd be rather difficult customization to do.
I'll forward that to the developer maintaining Roundcube in epesi, perhaps we'll be able to implement this as a new feature. I can certainly see the merits of having such feature.
Kind regards,
Arek