I am able to send a single email message to a Google Workspace Business Standard account label containing hundreds of email addresses (301 to be exact) with no problem when I use the Gmail web interface. But when I try to send the same message to the same set of 301 email addresses using the same Google Workspace account in Thunderbird, I get the attached error. The link in the error dialog is apparently incomplete, so it leads nowhere. The daily (24-hr rolling period) limit on a GW Business Standard account is 2000, so this is clearly under the limit (the only 2 messages - from GW online and TB - sent to that many recipients that day). It could be that Google imposes a limit on 3rd party email clients that is causing this, or it could be something with TB. Does anyone know which it is? Has anyone else had the same problem? Thanks for any info you can provide!