@ninjasl I dont know why you get error with Gmail.
Have you tried to change the selection from Gmail to SMTP and insert in the host field

{imap.gmail.com:993/imap/ssl}INBOX

Do you have the possibility to try to configure maybe a your custom domain email or a different email provider?

Please read also this two topics:

Delay in replies from the UVdesk staff members and developers Fix problems with UVdesk