What is the size of your Inbox, assuming Inbox is the folder you delete the message from?

What is your anti-virus software?

Anti-Virus is the default from Win 10. How to see the size of the Account?

I have 5 accounts. In total over 6 GB. I don't think it is because of the size.

After I inbox ---> Properties ---> Repair Folder it works again like expected. But as I said, after relaunching it's slow again.

Right-click Inbox in the folder pane - Properties What is 'Size on disk'?

Try to start Windows in safe mode with networking enabled. - Win10 https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode

Does the problem go away?

Can't check the Windows in safe mode with networking enabled, because I only have WiFi here.

By the "Size on Disk" you mean the sizes you can see on the screenshot?

Empty the 'Papierkorb' folder. You have more unwanted deleted rubbish emails in that folder than in the rest of entire storage of folders with good emails. It's the trash folder for unwanted emails, not a storage folder. It's useful because if you delete in error, you can recover the email. But, Trash should not be used as a non trash save everything just in case folder. It could be taking ages because you are having to open and write to what is a large file of unwanted stuff.

Inbox has a small size and so I would assume you have been compacting the folder.

re: Can't check the Windows in safe mode with networking enabled, because I only have WiFi here. Yes, you are right, as default that is what Windows OS does, but it can be setup to work.

in Safe Mode with Networking, limited drivers are loaded which will not allow you to utilize your wifi functionality. However you may sort this issue by enabling drivers and services. To do so follow the steps below:

Drivers: While in Safe Mode with Networking, open Device Manager. Then double click to expand Network Adapter, right click on the driver and select Enable.

Services: While in this mode, open the Services page through Run Command (Windows button+R). Once opened, type services.msc in the dialog box. Or type 'services' in search and select 'Services app'.

This will open the services page. Scroll down, locate and select WLan AutoConfig and set the Status to Start.

To Empty the 'Papierkorb' folder. Right click on 'Papierkorb' folder and select 'Empty Papierkorb' or it might say 'Empty Deleted'

Emptying the trash folder solved my issue!

You are totally right! :D Trash is trash and not an archive folder.

But why outlook have no issues with the big trash folder? Everything is very smoothly on outlook.

hi. i had the same deleting slowness problem and following what's in this tread it looks like now it is solved. though, after emptying the trash folder in my account (i have two, i.e. the main one and one secondary, which i left untouched) i find that the outbox (sent) in the main is now empty too!!! :-((( now, as i was born in the tubes era i don't deem myself totally dependable on pcs, but i am reasonably quite sure that i didn' do anything to this folder... any explanation for this? at any rate, is there a possibility of recovering the deleted messages/undoing? thanks, and have a great day...and a stay safe! cheers, bobo romeo.

bobo53

Each mail account should only have one 'Trash' folder, which may be called another name such as 'Deleted' or 'Bin' etc depending upon the server if using an imap mail account.

re :i find that the outbox (sent)

Please be careful with names of folders as some have specific meaning and function. It is important to state the name of the folder and whether it is a Pop or Imap account folder.

The 'Outbox' folder is usually located in 'Local Folders' mail account and it serves as the 'Outbox' for all mail accounts. This 'Outbox' folder is used for emails that have been composed and 'Send Later' option used. So the emails are ready to be sent, but not actually sent just yet. A right click on the 'Outbox' folder offers the option 'Send unsent messages', if selected then all the emails held in the 'Outbox' are sent and the Outbox now looks empty. If you exit Thunderbird or choose to go into 'Offline' mode and there are emails held in the 'Outbox' folder, you may be prompted to 'Send unsent messages' first.

There is also a 'Sent' folder for each account, which some imap accounts may find it is called 'Sent Mail', but it depends upon how the server named that default folder. The 'Sent' folder contains emails that you have actually sent. Generally, this folder should not get emptied. If an imap account then it could get emptied if emails were deleted off the server via webmail account or another imap account accessing server or by the 'Retention Policy' setting on the 'Sent' folder (right click on Sent folder and select 'Properties' ) or the account 'Retention Policy' settings. It could also get emptied if an Anti-Virus product quarrantined the folder.

But, if the settings I mention above do not show anything, then this would need further investigating to resolve, in which case it would be better if you asked your own question as the person who originally created this question does not need a load of emails being sent to him about someone elses issues.

thank you very much for your thoroughful answer. actually, you remind me that i have just cleaned up my imap mail web account, and it is possible that together with the obsolete received mail i deleted also the "sent" mail folder on it, and as you mention this possibly emptied also the "sent" folder in thunderbird . but, i thought that thunderbird should keep messages on its own independently of what is done on the website. wrong? for your information, in right-clicking "sent"- "preferences" the retention policy is set as "use the account settings": does it mean the settings in th-bird or on the webmail server? i understand that for this further enquiry i should address a new topic, but please understand that i would rather prefer not to interrupt our thread and start it all anew. thank you and have a great day, bobo.