Short answer
HubSpot deduplicates contacts by email, so two contacts cannot hold the same address. A contact can have additional email addresses; HubSpot's KB says if Save is disabled, the address is already on another contact. Segment filters, reports and workflows use only the primary email. Salesforce syncs only the primary email.
1. On the record
Emails are edited from the contact record in my demo portal.
2. For shared inboxes
Create one contact for info@ style addresses and associate the real people as separate contacts at the company.
3. Related
Second deal for the same contact.