You can email one person or a whole segment, using a template so the message is consistent and personalized. Here's how.
Build (or open) a segment of the people you want to reach — for example, "first-time donors this year."
Use the segment's Email action.
Pick a template (or start from a blank one). See Email & Document Templates.
Fill in anything the template asks for at send time, such as a date range.
Preview — CoolFocus shows how many people will receive it and lets you check a sample.
Send. The email goes out to everyone in the segment who has a valid email address.
Open the donor or contact's record and use the Email action there. Same flow — pick a template, preview, send — just for that one person.
Each recipient's email is personalized from the template's merge fields (their name, giving totals, and so on).
People without a valid email are skipped automatically, so you don't get errors for missing addresses.
Every send is recorded as correspondence on the person's record, and you can review the batch — who it went to and the delivery status — from its history.
Email is delivered from your organization's verified sending email if one is set up; otherwise a default address is used. Replies can route back to your organization.
Some teams also send text messages to a segment. That works similarly from the segment's actions where enabled. For day-to-day one-to-one texting, use the Inbox instead.