Regarding your flood of unwanted emails arriving, you may want to set up some filtering rules to make them ‘disappear’.
The rules I had in place with ATmail managed by Internode were all copied over to TMC managed ATmail. I did not rely on filtering rules provided by Internode. I set up my own.
Hardly ever see any junk and spam coming in. Just the sophisticated emails that need to be checked. Maybe a few of those a week.
The longer an email exists (and is used for logins and/or registrations), the more likely it will attract spam and phishing emails. It may take some time, but it will happen.
Lots of businesses lose control of their user databases, or sell the information to others. This does lead to spam emails. For examples of these breaches we have several topics on this site, the latest can be found at Data Breaches 2024 to 2025 (it has links to the previous topics as well). There is some discussion about tightening our privacy laws as well, this is being discussed by Government to help give users better protection regarding how our data is used by businesses that we give our details to.
I use disposable email addresses wherever I can, if one becomes a problem I can just block it. If the site is still important to me, I supply a new disposable address and let them know that my previous address has been compromised. Filtering (as @Gregr has mentioned) of the emails for any address I can’t change (there aren’t too many of those), stops most bad emails getting through from those.
Too right, filtering is helpful. I’ve used it to kill ads coming in from Africa, Russia, etc. The TMC ones are coming from everywhere and the only phrase I’ve blocked so far is “The Messaging Co Team”. I’ve just been forwarding 'em to TMC (who surely should be acting against this). But not a peep out of them…
Sounds like a useful idea, but my life has too many complications already… 
Disposable emails get sent to your main email account. When you need an email address for a site/login, you create the disposable address for that site (and only that site), the email sent from that address gets forwarded to your normal main email address without the sending party ever knowing your real address. If you start getting spam through that address, you will know what Company/site sold or lost your details.
If it is a problem or a site you don’t care about, you simply block or delete the email address and no further emails are sent through. Once a disposable address is deleted then no need to worry about storage size either on your device or on your email provider’s servers, the emails just go into the ether/blackhole as they never reach the email server in the first place. There are some companies that supply the disposable addresses to a user who wants to take advantage of the system. Some are free others are pay for use. Some examples follow
Currently free service (paid service has extra benefits) with unlimited standard aliases
Or
a limited number of aliases for free (10 in the free version)
If using Apple there is
Hide My Email
Another service with limited free aliases (3 in the free tier), 50 in the middle tier, unlimited in the ultimate.
It is very easy to set up email filtering in ATmail. Don’t rely on the email provider to do it.
Just go to settings->mail->email rules
One of the first things I did was block anything coming in from all these new-fangled suffixes like .icu, .info, .biz, and that cut spam to a trickle. And then blocked mail coming in from any source that I didn’t want to get mail from that wouldn’t allow unsubscribe.
Simply not a problem at all for me. And no reliance at all on the email provider.
My attitude is I simply don’t care who knows my email addresses. It is open knowledge. I have no control over who knows them. People share them. Businesses sell them. Hackers get hold of them. It is just a postbox name on some email server somewhere on the Internet.
But I control who can try to send me stuff.
I tried unsuccessfully to find email rules in Thunderbird but have found them on the relevant webmail page. Thanks for the advice.
They’re called “filters” in Thunderbird.
Thunderbird has automatic junk mail filtering.
Go to:
Setting>Privacy (Tab)>Junk
Help for using these setting can be found here:
The training also works over time if one receives regular spam from the same source.
There is also the ability to use one of a number of spam filtering sites by setting the Junk settings for each account to whichever junk filtering service you prefer or want to try. I would suggest that moving Junk messages to a spam folder rather than delete to make sure a user can check if the email is actual junk or not before deleting.
For best filtering, as you noted it is best to train the filters if using the built in service of Thunderbird. This means that at the beginning it is best to allow a modest amount of junk into the inbox, so it can be marked as junk to help train the filter faster.
