I've run into similar issues with a similar setup. It's frustrating. You can convince gmail user A to whitelist your messages, and so they'll get through to user A, but gmail user B probably still won't see messages from you unless you tell him to dig them out of the spam trap. And your messages to A might still be classified as spam if they have attachments or hyperlinks in them. (Even if you've been corresponding with A for several years!)
Once upon a time, to send email, you needed to use SMTP. Now, you must use SMTP, from a IP block that isn't categorized as residential, and which has never before had any association with outgoing spam, and you also must implement several ad-hoc identification protocols like SPF and reverse DNS. You should also use a domain name that you've owned for some time and which is not expiring soon. Every system to which you want to send mail will give different weights to all these signals. If they don't like you, their behavior is to report successful delivery and then silently hide messages from their intended recipients.
Spam is no fun, but the present situation is pretty weak too.
Once upon a time, to send email, you needed to use SMTP. Now, you must use SMTP, from a IP block that isn't categorized as residential, and which has never before had any association with outgoing spam, and you also must implement several ad-hoc identification protocols like SPF and reverse DNS. You should also use a domain name that you've owned for some time and which is not expiring soon. Every system to which you want to send mail will give different weights to all these signals. If they don't like you, their behavior is to report successful delivery and then silently hide messages from their intended recipients.
Spam is no fun, but the present situation is pretty weak too.