Multiple chrome users, need help

Hey guys, I need help. I want to use mail merging like: Gmass, YAMM and others and use multiple gmail acounts. I tried to run 2 gmails with different mail merging on same IP, even same browser and both of them got banned at the same time, it happened after some weeks of using it, but it happened straight away on both. So for me it looks like they were somehowed linked, otherwise why both of them would get suspended at the same time?

So im thinking what to do in order to avoid this for the future.

Should i use different chrome users and for each user have a proxy? Or should i use chrome portable + each portable has ip?

Or maybe i should even use android emulator like bluestacks with an ip for each google account? I really need advises on this. Thanks!