I received a notice from my hosting provider, InMotion, that they are going to roll out Mail Channels for all of their accounts on shared servers early next year. Due to a conflict I had with their standard spam filter, Spam Assassin, I had them remove that from my account. I don’t see a Mail Channels icon and I think it might be due to the removal of Spam Assassin. If I request Mail Channels to be installed on my account, will there be an issue with Spam Sieve due to software upstream of Spam Sieve filtering emails? I have a great deal of trouble sending emails to Yahoo and AOL accounts - they block my mail server on a regular basis - so the outbound mail feature of Mail Channels appeals to me. I have not yet reached out to InMotion regarding this new feature they are implementing.
The outbound filtering will probably make it more likely that your sent messages get through.
The inbound filtering doesn’t affect SpamSieve, but you may find that MailChannels blocks some good incoming messages and removes them without putting them in the Junk mailbox. Since they are not even in the account, SpamSieve cannot rescue them for you. If that becomes an issue, maybe they can configure it to only do outbound filtering.
After installing Spam Sieve, I disabled Spam Assassin and several years later, InMotion, without my permission, reactivated Spam Assassin. That caused huge problems with Spam Sieve because Spam Sieve wants to be the only spam filter. I complained to InMotion and they removed Spam Assassin from my accounts. Now, they are going to switch to Mail Channels, which will save them money and may improve deliverability. The “cost” to me is that I have to modify my DNS settings because both accounts are on CloudFlare. What a hassle!!! 
I’ll talk to them on Monday to see what my options are.
It’s fine to use SpamAssassin and SpamSieve together.