Looks like this may be an unintended consequence of bug 1611624. In the log above what's happening is the login/authentication to yahoo is OK but yahoo doesn't send any capabilities with the authenticate response. Apparently the yahoo server doesn't like to send capabilities in quick succession or redundant capabilities since it had already sent them in the "greeting" when the connection is made within the TLS tunnel. Yahoo responds to the capability request after authenticate with untagged "Bye", the the "NO [LIMIT] and then drops the connection. Another possibility is that the capability request is too close in time to the next ID request and triggers the [LIMIT] error, but I doubt it. What I'm not sure about is how this manifests itself to the user? Is there just a pop-up error and then TB recovers and no harm is done, or does it cause some other problem? It appears from the log fragment above that an attempt to select the "Bulk Mail" folder was attempted but I'm not sure what happens later in the snipped part of the log. The URL may be retried and succeed the 2nd time (i.e., no yahoo complaints about LIMIT). It might be helpful to attach a more complete log using the "Attach new file" button above.
Bug 1727971 Comment 2 Edit History
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Looks like this may be an unintended consequence of bug 1611624. In the log above what's happening is the login/authentication to yahoo is OK but yahoo doesn't send any capabilities with the authenticate response. Apparently the yahoo server doesn't like to send capabilities in quick succession or redundant capabilities since it had already sent them in the "greeting" when the connection is made within the TLS tunnel. Yahoo responds to the capability request after authenticate with untagged "Bye", then the "NO [LIMIT] and then drops the connection. Another possibility is that the capability request is too close in time to the next ID request and triggers the [LIMIT] error, but I doubt it. What I'm not sure about is how this manifests itself to the user? Is there just a pop-up error and then TB recovers and no harm is done, or does it cause some other problem? It appears from the log fragment above that an attempt to select the "Bulk Mail" folder was attempted but I'm not sure what happens later in the snipped part of the log. The URL may be retried and succeed the 2nd time (i.e., no yahoo complaints about LIMIT). It might be helpful to attach a more complete log using the "Attach new file" button above.