This article lists some alternatives to DreamHost's Webmail service.
Hosting with non-DreamHost mail
DreamHost offers Google Workspace.
Google Workspace is a collection of apps to help organize and simplify your organization's workflow and includes a mail service (Gmail). For more information about using Google Workspace at DreamHost, see the following article:
Using Gmail as a Webmail client
Gmail's Mail Fetcher POP3 client can connect to your mail accounts and POP the emails off of the DreamHost server into your Gmail account. Gmail can also use SMTP to send mail from your mail account.