Yes, you can use HubSpot without Gmail.
If you use MicroSoft Outlook (on PC only) you can instal a plugin that will make your life easier. More info on the Outlook Plugin.
If you don't use Outlook, or use a Mac (Outlook on a Mac won't let you install plugins) you can BCC the CRM and your contacts and emails will be added to the CRM. More info on using BCC and Forawrding Emails.
Or, you can send email from inside the HubSpot CRM.
Monday - last edited Monday
I'll have to read it over when I'm not so tired.
It's too bad you guys don't have an add-on for Thunderbird.
So I already e-mailed one lead & only now put him into the CRM. Is there any way to tell the CRM I already e-mailed him?