tl/dr: This is your hosting company's problem, not yours. You'll have
to contact them to get it fixed. Their security policies shouldn't
lock you out of your own account. They need to do security better.
You already have some answers that I agree heartily with and which cover the technical aspects of this, but I'm throwing in another answer to cover a "business" item. Here you hit on the crux of the issue:
However as a result of the authentication failures, my hosting
provider keeps locking the email account.
In otherwords, the problem isn't your problem. You have done everything you can to secure your account on someone else's mail server - you are using a strong password that can't be brute forced. The underlying issue here is that your hosting provider has implemented a bad security policy. As @vidarlo mentioned, this is just the background noise of the internet. Your hosting provider should know this. Unfortunately their chosen response has the side effect of locking you out of your account.
In essence the combination of your hosting company's choice of security policies and the standard password scanning that happens to every server on the internet has resulted in a denial of service (DoS) of your email. If your email went down because someone attempted an actual DoS of your hosting provider and filled their networks with useless bandwidth, the solution would be quite simple. You wouldn't be here asking what you can do to fix the problem - you'd be talking to your provider and asking them to fix it. After all, the whole point of using a third party email service provider is for them to provide you with a service. If you are not being provided with that service, either because their servers went down, or because their network is crippled by a DoS, or because their security policy is overly zealous and locks you out of your account, then the only real solution is for your hosting provider to fix it and provide you with the service that you are paying them to give you.
Many questions we get here are the result of people ignoring security all together.. However, there are plenty more examples of people trying to do security but just doing it wrong. This is one of the latter. Therefore, you definitely need talk to your hosting provider and get them to fix it. If they can't provide you with the service you are paying for, then you need to switch to a provider that will (although hopefully it won't be the kind of provider that simply doesn't do security at all).