Looking for Remote Work Advice

Greetings all! I just started a new job working remotely. In this position, I have 2 separate computers with 2 separate email addresses. I work for company A but much of my work is done on company B’s system which has its own email address (hence the 2 computers). There are emails coming in to both email addresses under the same topic - internal discussions come in under the company A’s email and general discussions are coming in under company B’s email address. I’m overwhelmed trying to organize and keep everything together! Any ideas on how to best manage this?