ResponseCode 421, 4.7.0 [TSS04] Messages from 135.84.80.216 temporarily deferred due to user complaints - 4.16.55.1 to sky.com and yahoo.co.uk addresses.

I understand that your "free tier" may keep suffering from people signing up to spam Yahoo customers, and I see from the last two years of history on this forum that ZOHO keep suffering from this problem.

However, my question is:
Are the business tier outgoing servers different from the free tier ones?
i.e. Would it be worth me upgrading to take advantage of this?

Thanks