When you send an email from the CRM with a connected inbox, the From address defaults to your user email address. You can connect more than one inbox to HubSpot if you want to send emails from the CRM with other email addresses.
Anemail alias is an alternate address that points to a user's existing email account. If you want to send emails from an email alias, you can do so from the CRM depending on your email provider. Or, you can manually add the email alias in your Profile & Preferences so emails sent outside of HubSpot can log to the CRM.
When you connect your Gmail account to HubSpot, HubSpot automatically detects the Gmail alias and adds it as a From address. You can select the Gmail alias in theFrom dropdown menu in the email composer:
Alias support for Office 365 and IMAP connected inboxes
If your inbox is connected to HubSpot using Office 365 or IMAP, you cannot send emails from the CRM using an email alias. You can use the alias to send emails from your connected email address and log them to HubSpot using the BCC address or the HubSpot Sales email extension. The aliases are not automatically added to HubSpot when connecting your inbox with Office 365 or IMAP, so you must add the alias to your Profile & Preferences:
In your HubSpot account, click your account name in the top right corner, then click Profile & Preferences.
In the left sidebar menu, select Security.
In the Email Aliases section, click Add email address.