There is no feature to automatically reply to incoming e-mails.
If you set "automatic forwarding", you can automatically forward the e-mail to another e-mail address if the specified conditions are met.
You can forward e-mails sent to you during a vacation or a business trip to another person.
For details, refer to Configuring Automatic Forwarding.

You can export e-mail data in UNIX mbox format or eml format file.
For details, refer to the method to export to files.

To move spam e-mails to a specific folder, select keywords included in the spam e-mails or sender names and save them as filter conditions.
For details, refer to Filter settings.

You will be able to start sending and receiving e-mails after adding information for the Gmail mail server and your e-mail account.
For details, refer to the article Can I use Gmail in Garoon? in the FAQ.