Use Gmail to import everything into one account. https://support.google.com/mail/answer/21289?hl=en

It's a good idea to keep accounts separate though if they are for different purposes. You can setup filters in Gmail for important emails. I also find it very helpful to use Google Chrome's User Accounts to easily switch between different Google accounts. Feel free to call me at 812-650-4405 if you want to discuss this more.

With Gmail you can also set reply base on which email was sent. So example if they emailed bob@domain1.com you can set to to reply back from that email and not your main Gmail or Google Apps email.