Vox Telecom email address spam listed by Gmail

Vox Telecom is the service provider for my primary email address. All emails sent from this email address to Gmail recipients get sent to the recipients' spam folders.

I have made numerous calls to Vox to ask for assistance and they have had little ability or interest to actively assist in resolving the issue. One technician admitted to me that Vox have occasionally been having issues with emails being spam listed by Gmail, while another told me that Vox can only assist me if more of their clients start having the same issue since this has happened on a large scale with other webmail service providers before. They have suggested I download software called "Malwarebytes" and even purchase third party software (on top of the monthly service fee I pay Vox). What I gather from these conversations is that there is general awareness among Vox technical staff that some emails sent from their servers may be spam listed by Google but they expect the client to deal directly with the webmail servers.

I cannot be expected to contact each person over the telephone and tell them to check their spam folders (which is also something Vox suggested). I pay a service fee for bad service and to be accused by Vox staff of sending out spam. I am considering to cancel my account with them and migrate to a more professional and reputable service provider.