all emails are in mbox file under different folders, which are inside the TB-profile folder.
in your newer TB goto main menu > Help > Troubleshoot Information > about:profiles > "Root" Directory > write down the full PATH of root directory.
the last sub-folder in the root dir full path, is the TB-Profile for newer TB.
remember/write it.
we will call this last sub-folder "new-TB-profile".
in macOS, TB-profile(s) are here:
"~/Library/Thunderbird/Profiles/"
that is usually here:
mac default volume : "/Users/<MacOsUserName>/Library/Thunderbird/Profiles/"
other sub-folders under above location, which are not "new-TB-profile", are your older-TB-profile.
exit newer TB.
copy mbox files inside "Local Folders" of ".../new-TB-profile/Mail/Local Folders/"
from the older-TB-profile.
start newer TB.
inside sub-folder under your "Local Folders", you should find older emails.
don't rename that older email's sub-folder , instead first create a correct named (another) sub-folder for those emails.
select all older emails & move them into correct named sub-folder.
above way, move other older email sub-folders into correct sub-folders.
IMAP based mail-accounts have all emails in remote mail-server , those do not need to be copied into new TB.
once you add IMAP based mail-account in new TB, those emails will re-appear.
POP based mail-accounts have all emails in local computer , those need to be copied into new TB.
copy emails of POP mail-account's MBOX file(s) into a sub-folder under your "Local Folders" in new TB,
restart new TB.
those will appear inside subfolders under "Local Folders" , then you can move those emails into correct POP mail-accounts in new TB.
More/Related Info:
• Disable AV/FW/SS software mail-protection OR enable+add+allow EXCEPTIONS in it & add mail-server names/address . Some AV/SS creates insecure proxy/gateway for scanning/checking emails, but there are other secure way to scan/check emails . Please make sure the option "Allow AV to Quarantine email" is selected inside TB, and make sure your AV/SS is set to Scan all files on access.
• Regain old data , in Windows : by using downgrade process, or by using a Second-TB, or by using manual file-transfer,etc).
• Downgrade TB in macOS: downgrade by using second-TB , upgrade/downgrade TB.
• AT&T , ATT-Yahoo related settings for TB.
• Yahoo , ATT-Yahoo related settings for TB.
• Microsoft Hotmail/Outlook related settings for TB.
• Convert MAB/mork or SQLite based Address-Book into other format, mbox email files into other format.
• Disabled auto-update or update of TB : inside the linked page , click on the topside 1st link to goto the auto-update disable instruction page into another website.
all emails are in mbox file under different folders, which are inside the TB-profile folder.
in your newer TB goto main menu > Help > Troubleshoot Information > about:profiles > "Root" Directory > write down the full PATH of root directory.
the last sub-folder in the root dir full path, is the TB-Profile for newer TB.
remember/write it.
we will call this last sub-folder "'''new-TB-profile'''".
in macOS, TB-profile(s) are here:
"~/Library/Thunderbird/Profiles/"
that is usually here:
mac default volume : "/Users/<MacOsUserName>/Library/Thunderbird/Profiles/"
other sub-folders under above location, which are not "new-TB-profile", are your '''older-TB-profile'''.
exit newer TB.
copy mbox files inside "Local Folders" of ".../new-TB-profile/Mail/Local Folders/"
from the older-TB-profile.
start newer TB.
inside sub-folder under your "Local Folders", you should find older emails.
don't rename that older email's sub-folder , instead first create a correct named (another) sub-folder for those emails.
select all older emails & move them into correct named sub-folder.
above way, move other older email sub-folders into correct sub-folders.
IMAP based mail-accounts have all emails in remote mail-server , those do not need to be copied into new TB.
once you add IMAP based mail-account in new TB, those emails will re-appear.
POP based mail-accounts have all emails in local computer , those need to be copied into new TB.
copy emails of POP mail-account's MBOX file(s) into a sub-folder under your "Local Folders" in new TB,
restart new TB.
those will appear inside subfolders under "Local Folders" , then you can move those emails into correct POP mail-accounts in new TB.
More/Related Info:
• [https://support.mozilla.org/en-US/questions/1315734#answer-1373915 Disable AV/FW/SS software] mail-protection OR enable+add+allow EXCEPTIONS in it & add mail-server names/address . Some AV/SS creates insecure proxy/gateway for scanning/checking emails, but there are other secure way to scan/check emails . Please make sure the option "Allow AV to Quarantine email" is selected inside TB, and make sure your AV/SS is set to Scan all files on access.
• [https://support.mozilla.org/en-US/questions/1316147#answer-1372552 Regain old data] , in Windows : by using downgrade process, or by using a Second-TB, or by using manual file-transfer,etc).
• [https://support.mozilla.org/en-US/questions/1304550#answer-1352743 Downgrade TB] in macOS: [https://support.mozilla.org/en-US/questions/1317224#answer-1374579 downgrade by using second-TB] , [https://support.mozilla.org/en-US/questions/1318142#answer-1377801 upgrade/downgrade TB].
• [https://support.mozilla.org/en-US/questions/1315734#answer-1373022 AT&T , ATT-Yahoo related settings for TB].
• [https://support.mozilla.org/en-US/questions/1304518 Yahoo , ATT-Yahoo related settings for TB].
• [https://support.mozilla.org/en-US/questions/1316618#answer-1374784 Microsoft Hotmail/Outlook related settings for TB].
• [https://support.mozilla.org/en-US/questions/1317619#answer-1375337 Convert MAB/mork or SQLite based Address-Book into other format], mbox email files into other format.
• [https://support.mozilla.org/en-US/questions/1316147#answer-1372552 Disabled auto-update or update of TB] : inside the linked page , click on the topside 1st link to goto the auto-update disable instruction page into another website.
