Thunderbird Community Forum

Dear Thunderbird Support Team,

I am writing to report an issue with custom message tags in Thunderbird that started occurring around September 28, 2026 (likely following a recent update).

Issue Description: The problem applies to all folders (Inbox, Sent, custom subfolders, etc.) and is strictly isolated to user-created (custom) tags.

When I apply a custom tag to any email, the tag visually attaches to the message. However, as soon as I switch to another folder in the folder pane and then return to the original folder, the custom tag disappears completely.

Key Observations:

No Relation to Filters: This issue happens with regular emails in any folder, with no filters involved.

Custom Tags vs. Default Tags: This affects only custom tags created by the user. Default built-in tags (e.g., Important, Work, To Do) save correctly and persist after switching folders.

Timeline: All custom tags assigned before September 28, 2026, are still preserved correctly on older emails. The issue affects any new attempt to set a custom tag after this date.

Steps to Reproduce:

Select any email in any folder.

Apply a user-created (custom) tag to the email.

Observe that the tag is visually assigned.

Click on any other folder to switch views.

Return to the original folder — the applied custom tag is gone.

Could you please assist in resolving this issue or suggest a fix/workaround? Custom tags are essential for our daily email management.

Thank you for your help and support.

Best regards,

Ihor Hirnyi E-mail: ig@zrn.com.ua

Mamy w firmie dostęp na 6 stanowiskach do jednej skrzynki pocztowej, ale tylko na 4 z nich działają oznaczenia etykiet. To znaczy na jednym z 4 działających stanowiskach zaznaczam że sprawa z maila została zrobiona ( wybieram etykietę zieloną " zrobione") i pokazuję się to tylko na tych 4 a na pozostałych 2 nie widać tej etykiety, ani odwrotnie. Jeśli zaznaczę etykietę na jednym z dwóch stanowisk to nie widać jej na żadnym stanowisku. Etykiety mają wszędzie te same nazwy, kolejności i kolory. zainstalowane są na każdym stanowisku najnowsze wersje programu. a serwer nie ma poustawianych blokad

Hello, I use the 32-bit portable 153;2 version of Thunderbird. But now when I label a message according to my list of labels by color, the selected message returns to its original color. Labeling no longer works, even though old messages retain their colors well. Thank you for your response. Ph. Costes

I have quite a few tags and quite a few message filters which are set to add tags. In the last few days, although the rule will automatically add a tag when I run it, it seems to be being deleted again almost immediately.

I have deleted several now obsolete message rules in case there was some kind of stack overflow problem, and likewise removed several obsolete tags, but it seems to be still happening. Is there a maximum number of permissible tags and/or a maximum number of permissible rules that invoke tagging?

This is a new phenomenon to me. I am on the latest stable release of Linux Ubuntu and Thunderbird 153.2.0esr (64-bit)

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But, minutes later, the tag will un-apply itself, and I cannot figure out why. For some reason, an older message is staying correctly tagged with that filter, but newer ones un-apply the tag. This same filter and tag used to work just fine. Other tags on emails from the same source work fine, too.

Dobry den, vytvoril som si stitky - uhradene (zelena farba). Ked si stitkami oznacim spravy a potom sa prekliknem do ineho priecinka a vratim sa do toho predtym nazad kde som si to oznacil, zmiznu. Alebo ak zavriem program a otvorim nie su tam. Predtym ich pekne drzalo, teraz nie.

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Hello,

I have been using Thunderbird, but the tagging behavior has become erratic since version 153.

The phenomenon is as follows:

• Tags attached to messages are disappearing on their own.
• The tags disappear when I select a message or receive a new email.
• It does not occur with the default tags (such as "Important"), but only with the ones I registered myself.
• It also occurs in troubleshooting mode.

Is there a solution?

Regards.

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