Unable to write the email to the mailbox error message

"I tried checking the settings": what settings?

If you haven't set Norton not to scan incoming messages, you should try that.

Another possibility: if there is a message that keeps trying to download, or only one message downloads, delete that message via the email provider's web interface.

I checked all of the Aol mail settings but since I see many example of this problem, it is not Aol but Thunderbird. We've changed nothing on any programs, including Norton. Just yesterday the mail download stopped working. I'm not sure how to set Norton not to scan incoming messages and looked in that program. But isn't it important that it scan such?

I can't tell if there is only one message causing a problem but I did try an idea. I went back to the last email that successfully downloaded, than I went to the online mail server and deleted that and deleted the next message. I was then able to successfully download everything since then. Your suggestion got me to thinking that might work and it did.

Is this a typical problem with Thunderbird? Or is it random? I guess I'm trying to determine if there is something I need to do to make sure it doesn't happen again.

> Is this a typical problem with Thunderbird? Or is it random?":

It is a typical problem with antivirus programs. They sometimes flag a message but for some reason don't deal with them appropriately, so the download just locks up. If you can figure out how to set Norton not to scan incoming messages, change this TB setting; then you will be protected:

TB menu > Settings > Privacy & Security > Security > Antivirus > Allow antivirus clients to quarantine individual incoming messages is enabled.

It seems counter-intuitive but it works. What happens is that when you open a message, it opens in a temporary file in a folder where it can be scanned by the AV program. That way, the downloads continue.

I checked all of the Aol mail settings but since I see many example of this problem, it is not Aol but Thunderbird. We've changed nothing on any programs, including Norton. Just yesterday the mail download stopped working. I'm not sure how to set Norton not to scan incoming messages and looked in that program. But isn't it important that it scan such? I can't tell if there is only one message causing a problem but I did try an idea. I went back to the last email that successfully downloaded, than I went to the online mail server and deleted that and deleted the next message. I was then able to successfully download everything since then. Your suggestion got me to thinking that might work and it did. Is this a typical problem with Thunderbird? Or is it random? I guess I'm trying to determine if there is something I need to do to make sure it doesn't happen again.

I will summarize for you so you are not in the dark. Remove Norton and remove the problem. That is all. Or you can change the settings as was first suggested to you by Ed. This is not really a Thunderbird problem, despite the symptom appearing in Thunderbird.

Now to digress a little. You think it important to scan incoming messages. Microsoft apparently does not! They built an antivirus product that tests in the top tier at each antivirus test it is included in and is the number one end point product in the corporate world. Yet it ignores email entirely. Consider that before making assumptions about what is "necessary" I approached Symantec probably 15 years ago and asked them what was the purpose of email scanning. Their answer was "another line of defense". Putting sewerage in the moat is also another line of defense. However most of us dispensed with the moat centuries ago for defense and I do not know if the sewerage did much more than make the place small bad. . Personally I dispensed with antivirus scanning of email years ago and am untroubled with attacks from email. But I use Gmail and other top tier mail providers that provide malware scanning with their service. I also allow defender unrestrained access to my system,

So some things about antivirus products that frequently affect receiving mail and therefore Thunderbird.

• Scanning of encrypted connections. (Norton not Defender)
• Scanning of email (Norton and a host of paid antivirus products offering "another line of defense" not Defender)
• VPN (Norton and host of paid antivirus products trying to make themselves relevant offering a product way outside of the malware arena, not defender)
• Scanning in Thunderbird's profile folder. I think they all do this differently, but mostly unsuccessfully. Thunderbird maintains a lot of very large files. Often in the gigabyte range size wise. This takes quite a lot of time to scan when they are changed (think deleting an email, moving one or send one or even getting one.) What happens when scanning is occurring when Thunderbird tries to update a file is technically called file contention and like when you try and share a car parking space with another car the outcome is not good. Your experience is Thunderbird unable to access it's data and complaining about it.

To make Thunderbird lest prone of failure to access it's data you have to disable any form of scanning of the file in Thunderbird profile folder by the antivirus when they are accessed. Norton makes this hard as you have to exclude multiple sub folders as Thunderbird profile is a folder tree and Norton apparently can only comprehend one file of folder at a time, not a branch of a tree.

The instructions for that go like this https://help-iris.co.uk/PTP/ODL/ptp_technical_help/how_to_set_exclusions_within_norton_internet_security.htm

• Add a File or Folder Exclusion
• Open your Norton device security product.
• Click Security on the left menu.
• Click Open inside the Antivirus tile.
• Select the Exclusions tab.
• Click Add exclusion.
• Choose the file or the folder you want to skip.
• Click Open or OK to save.

Then there is the issue of Norton requiring you to reduce your security so they can hack your encrypted connections See https://support.norton.com/sp/en/us/norton-360/2.0/solutions/v20240108183457190

All of This so they can scan an inert text file that is being downloaded from the internet. Just to be clear. Email is transmitted as plain text. Images and attachments are converted to text before the email is transmitted and have to be converted back before you can view them. An email therefore can not do anything nor can it infect anything without you interacting with it.

Now to the security features of Thunderbird. Something those selling Microsoft products and antivirus programs do not want to talk about.

• Thunderbird blocks remote images by default. This has the effect of preventing the use of what are termed web bugs to track who and where emails are read. It is also something of a pain as those that use them also tend to make the whole email a huge web bug with almost everything being a remote image.
• Thunderbird does not allow scripting in the body of the email. This messes with a number of things folk tend to email, like interactive maps and videos from some sites, but it also prevents the infection of your computer just by opening the email. Something that can still occur in more "friendly" mail clients. I clearly recall Microsoft going into damage control around the year 2000 and telling everyone to not open strange emails, simply because their email clients ran the scripts in email. Not a problem if your mail client does not run scripts.
• Thunderbird "sanitizes" the HTML from an email to not perform security sensitive actions from the email. Additionally Thunderbird offers three ways to view an email. Plain text, simplified HTML and original HTML. The simplified HTML mode uses an even stricter HTML sanitizing approach that original HTML.
• Thunderbird has an option in setting to allow antivirus to scan incoming mail. This causes the incoming mail to be written as a text file in the system temp folder so the resident antivirus get a good chance to complain about it before it is written to the message store. As nothing in the file is "executed" it is perfectly safe and offers that "next line of defense" for those seeking it without all of the hacking and connection snooping that the third party product vendors have chosen as their preferred approach.

I am not issuing a guarantee that email scanning is not necessary, personally I do not use it. I feel my system is protected from everything but my own hubris. Even then, while I can not foresee the security issue that will make my opinion false, I do not doubt that it could happen and I accept the risk. In any discussion on antivirus products it is germane to keep in mind that the industry is largely based on fear and ignorance. Those that don't know pay for reassurance and few question the marketing advice they receive. Every paid antivirus I know of scans outgoing mail to find a virus that, by definition, it is unable to find or it would already have alerted you to an infection. They scan, waste computer cycles doing it and everyone accepts it because that is the way things have been done for 30 years. But is it the right thing to do? I think not. If my antivirus says my system is free of infections, where is this infection in the outgoing mail going to come from?

Sorry for the rant! but I also hope I did offer some food for thought and information you did not have.