Redirected emails bypassing spam filtering

[pnjfksx]

I have two domains setup where one was redirecting email to the other. The second one is filtering all email through a third-party service via MX records. The redirected email from the first one is not going through the filters. How do I make that happen?

Current:

Email2 --> Spam Filter Service --> Email2 Mailbox

Email1 --> Redirected to ---> Email2 Mailbox

Desired:

Email1 --> Spam Filter Service --> Redirected to --> Email2 Mailbox

Email1 --> Redirected to --> Spam Filter Service --> Email2 Mailbox