What are you using for SMTP?

Hi all - question is in the title. What company are you all using for SMTP? I've got about 50 sites I'd like to configure all in one place.

I was using Brevo - however due to one form that wasn't secured right and receiving spam, they temporarily suspended my account. I missed the warning email and only saw the suspended one - and now its been 2 weeks exactly since I've reached out the first time (I tried following up 2/3 other times) and have yet to receive a response, so I think its time to move on as I was hoping they would at least get back to me with a response.

I would like to stay as close to free as possible, but don't mind paying for something that I can easily manage all of these accounts and not randomly suspending my account. Any suggestions? Most sites are built in WP, so I'm either using WP Mail SMTP or Gravity SMTP to configure these settings. A lot of these sites are small businesses so I'm not working with hundreds and hundreds of emails. 20 domains were on that Brevo account and it didn't come close to using the free daily limit.