Channels
Mail goes out from each rep's own mailbox, not a shared sender. That one decision is what keeps cold outbound out of the promotions tab.
Connecting a mailbox
Settings, then Mailboxes. Gmail, Outlook and Zoho connect over OAuth: you click Connect, approve it at your provider, and you are done. Exchange connects over your organisation's web services endpoint, and anything else connects with SMTP and IMAP credentials.
Each rep connects their own. A workspace can have as many mailboxes as it has people, and nobody can read anybody else's.
What arrives in the inbox
Replies sync back and thread against the account, so a conversation lives on the company's timeline next to the calls rather than in one rep's mail client. Unread counts and notifications follow the same thread.
Replying
Reply carries the conversation forward the way a mail client does. If the prospect copied in a colleague, that colleague stays on the thread. The Cc list is shown and is editable before you send, and the line under the box tells you who it is actually going to, not just who it is from.
Dropping a Cc is silent. The rep writes "Hi Nathan and Zeke", Zeke never receives it, and nothing on screen says so. Reply-all is the default for a reason and it is the default here.
Suppressions
An address can be blocked for the whole workspace, and the block is case-insensitive: an address is one address however it was typed. Suppression applies wherever mail is sent from, including automated follow-ups.