There is no such capability in Thunderbird itself. You may be able to find an add-on to do this, but I don't know of any.

Your situation/requirement sounds like a legitimate use for a multiple profile setup. I usually try to discourage users from implementing these, but the easiest way not to service an account is to not install it. So, two profiles; one for you, one for work. But neither of these will provide your complicated variable scheduling. ;-)

https://support.mozilla.org/en-US/kb/using-multiple-profiles

I am not at clear what you wish or expect to achieve by fetching mail at different intervals. With IMAP, it tends to come as it arrives, not when your email client specifically requests it. If the account has high traffic levels, you'll be hit with a big backlog when you do access it, slowing everything else down. If it isn't busy, why worry about how frequent the updates are? Or maybe you have a slow and expensive connection and wish to ration and control its bandwidth consumption?

All of my accounts are on 10 minute intervals (where permitted; some stipulate 15 minute minimum polling interval) and I simply ignore those I don't need to read. ;-)

Many thanks for the answer :)

There is no problems for the network traffic. The problem is due to the icon alert: when arrive an email, thunderbird show the icon of the new mail: but if I am on Sunday, I receive the alert o a new mail also if it is an email in the "working box account" (that I ignore on Sunday). So If I ignore the alert, may be that I receive an email on the "personal box account" and I don't see it because the alert is the same.

Which is the file where is stored the information about the account setting of "Check for new message every xx minutes"? I can make a batch procedure that replace the file on Sunday: do You think it is a good idea? Or I can generate some problems?

Many thanks Gerardo

Umm yes.

The settings are stored in prefs.js, so you could swap various copies of this file in and out.

However, the system will load prefs.js, then, if present, user.js , so you can set up just your changes in user.js .

The sort of line you need to look for is like this:

user_pref("mail.server.server14.check_time", 10);

You'll need to do some research to identify which of your accounts is which.

Search for the account's email address: user_pref("mail.identity.id10.useremail", "xenos@example.com");

Use the id number to locate the account number: user_pref("mail.account.account29.identities", "id10");

Use the account number to find the server number: user_pref("mail.account.account29.server", "server14");

Finally, you can then use the server number find the account's time setting: user_pref("mail.server.server14.check_time", 10);

This last entry may not exist, if you have never changed the setting from the default 10 minutes.

Do be careful with your typing and copy/pasting; if the file fails the syntax parser it will silently fail.

And make sure Thunderbird is shut down when you do the swap. If it's open, it may overwrite changes, and in any case, it only reads the settings file when it starts up.

Maybe it would help if you used an add-on to issue an alert based on the receiving account, or the sender etc.:

https://addons.mozilla.org/en-US/thunderbird/addon/mailbox-alert/

https://addons.mozilla.org/en-US/thunderbird/addon/new-mail-attention/?src=search

https://addons.mozilla.org/en-US/thunderbird/addon/tonequilla/