re : 1. TB doesn't respect setting called "Sync last x days of emails"

It's a bit of an odd one to get your head around, but it syncs last x days every day which means the number of days that are synchronised increases every day. As each day occurs then previously downloaded emails get marked to say it's ok to remove when compacted. They cannot be auto removed because that comes under a delete type of function and you do not want an auto deletion to occur. To keep the number refreshed you have to compact the folders.

So please compact your folders now. File > Compact Folders

Do not do anything whilst it's compacting. Then check on the results.

re :2. I have changed login info on my CalDAV calendar so I wanted to remove the old ones and add the new one. However the old one wasn't somehow properly removed from my Ubuntu online accounts and TB keeps ghosting me to enter login info of account that doesn't exist anymore.

Check the stored passwords:

• Settings >Privacy & Security
• Under passwords section
• click on 'Saved Passwords'
• Click on 'Show Passwords'

See if there is a mention of the old calendar select to highlight and click on 'Remove' click on 'Close'

re : 1. TB doesn't respect setting called "Sync last x days of emails" It's a bit of an odd one to get your head around, but it syncs last x days every day which means the number of days that are synchronised increases every day. As each day occurs then previously downloaded emails get marked to say it's ok to remove when compacted. They cannot be auto removed because that comes under a delete type of function and you do not want an auto deletion to occur. To keep the number refreshed you have to compact the folders. So please compact your folders now. File > Compact Folders Do not do anything whilst it's compacting. Then check on the results.

It's not exactly what I meant. A fresh TB install, logging into my IMAP account with the default last 60 days of emails setting started downloading emails all the way from 2015 or so.

re :2. I have changed login info on my CalDAV calendar so I wanted to remove the old ones and add the new one. However the old one wasn't somehow properly removed from my Ubuntu online accounts and TB keeps ghosting me to enter login info of account that doesn't exist anymore. Check the stored passwords:

• Settings >Privacy & Security
• Under passwords section
• click on 'Saved Passwords'
• Click on 'Show Passwords'

See if there is a mention of the old calendar select to highlight and click on 'Remove' click on 'Close'

The password isn't there any more. I think it's somewhere else: either different email client or Ubuntu itself.

re :"Sync last x days of emails"

I'll try to explain a bit more on how it works.

Synchronization is about downloading the full message bodies for offline use. Meaning it would be possible to read emails even if you went into Offline mode. it's also useful if you need to create a backup of emails. This synchronise x number of days is not limiting the download of message headers.

Senario 1: If you selected 'keep messages in all folders....' meaning all folders could download full copies AND you clicked on 'Advanced' button and ALL folders were selected then you would get downloaded full copies of all emails in all the folders selected. But if you also selected 'Sync last 60 days of emails', then only the last 60 days of emails would get fully downloaded and all the others would only get headers downloaded.

So you will see Message List showing all your emails, but those older than 60 days would only be headers.

Senario 2: If you unchecked /did not select 'keep messages in all folders....' and you clicked on 'Advanced..' button to make sure NO folders were selected; it means it is not possible to download full copies of any emails, so everything downloaded is just headers. Then nothing is going to synchronised. In this situation, the 'Sync last x days of emails' option is rendered useless because no folders are being synchronised.

Senario 3: If you unchecked /did not select 'keep messages in all folders....' AND you clicked on 'Advanced..' button and selected/checked specific folder like 'Inbox', but did not select any other folder. Then the 'Inbox' folder will get synchronised to download full copies and all other folders would not get synchronised, so will only download headers.

In this situation, the 'Sync last 60 days of emails' option will now only synchronise the last 60 days of emails that are in the 'Inbox' folder. All older emails in Inbox would only download headers.

Basically, if you tell Thunderbird not to download any message bodies and you have not selected to allow full download, you can't limit the no. of message bodies to be downloaded to 'the most recent x days' because no message bodies are being downloaded. You will still see a list of all emails.

Downloading only the headers means a huge amount of space is saved yet it allows access to read the email. It would get retrieved from server on demand and stored in a temp cache to faciliate viewing.

Hope this helps to clarify what is occuring.

More info: https://support.mozilla.org/en-US/kb/imap-synchronization

OK so I have selected the folders I wan to sync and left the number of days to 60. But first of all, and that is what seems to have solved both of the problems, created a new Profile and imported only the settings, but not the saved emails and calendars from the previous one. Then I added the new calendar account manually. Thunderbird stopped freezing and asking me for login info of the old calendar. This was the solution.