That is the default for VPNs. Look at the settings for a bypass of email checking.

Thunderbird is just a client, it's not an e-mail provider. So you're wrong, they don't send this message.

There's no bypass of email checking in Mozilla's VPN software that i can find...so where is it???

See https://www.mozilla.org/en-US/products/vpn/resource-center/split-tunneling-with-mozilla-vpn/

That's a temporary fix...thanks. But it's not what I want so next month I'm going back to my old VPN...sorry Mozilla VPN can't handle my email accounts...

Hello there

Mozilla VPN seems to be a good kind of software. It blocks in various ways and are having a strong security capability. And Is user friendly to the user environment. The network is some sort of smaller then their big brothers like McCafé or other that s why the server might could be giving some blocking features for like users as you that like to use the VPN for strong internet usage.VPN Mozilla could collect some id information. Other browser functions from add ons or add ins can block the good use of that vpn Mozilla.If you decide to stay you might check these setting before using the Mozilla VPN again.yes Mozilla VPN could have some connection problems please read the manual wisely.

Greetings googlethunderbird.

If you say so...I'm still going back to my old vpn service...never had these issues before...I'll pay a tad more but it's worth it...

My Thunderbird is also blocked from receiving new email when Mozilla VPN is active. I added Thunderbird to the Exclusion list but the problem remains. This started a few days ago. I suspect this and other problems that have been happening may be related to the issue of Youtube's plan to promote universal consumer age identification (when such a scheme is virtually impossible to enforce). That is not the issue, though. Mozilla VPN is the least troublesome VPN I have tried so far. I also tend to trust Mozilla not to have an agenda other than the grand service of open source. I cannot envision the Mozilla team scurrilously providing user data to the government or other third parties for a pinch of extra profit, as many other VPN providers are reported to have done and continue to do. Every other VPN has presented contradictions and required compromises that I was not willing to make for a product that charges money. (I wonder how Volvo owners are feeling now that they have to pay rent to be able to use their heated seats and air conditioning. Welcome to the world of "we own nothing" and "they own everything". LEXX for short.) This very new email blockage is the only real problem I have had with Mozilla. There is some issue with the VPN not staying on or not starting up in Android properly, but I do not browse using my phone so I don't care. I am not one of those droids with my face glued to my phone 24/7. I read actual books. Back to the issue. Having to disable VPN for the few seconds it takes to get email is only a minor inconvenience. I do not expect this to become a red hot issue for support. But I expect it to be an issue, because the product is thus not perfect. If it were my product, then that imperfection would drive me to distraction. I would expect no less of anyone who dreams of bringing something useful into the world. Perfection or nothing. I hope Support works on this with all due haste. Thanks for your time.

Addendum: after approving my computer's ability to receive updates from this thread, I realize the Mozilla VPN is not completely blocking Thunderbird access to my ISP email service, but slowing the connection so much that timeout is inevitable. This is not a full blockage issue. It is a bottleneck or throttling issue. I don't know if that helps but it does make it different.

I solved the problem...I dropped Mozilla VPN...