Addons to transfer emails from the client to the server

I have an add-on for Thunderbird that archives emails in my management system. After the latest August update, on some devices, the email is not arriving complete at the server. This is the script that handles the file transmission:

var formData2 = new FormData();
formData2.append('autoriz', 'tuttok');
formData2.append('annox', annoy);
formData2.append('mesex', mesey);
formData2.append('giornox', giornoy);
formData2.append('idx', idx);
formData2.append('file', data);  // 'file' truncated

fetch(url, {
method: 'POST',
body: formData2,  // Pass the FormData as the request body

})
.then(response => {
if (!response.ok) {
throw new Error('Error in the request: ' + response.statusText);
}
return response.text();  
})
.then(responseText => {
console.log("send_email_auto2 " + responseText);

})
.catch(error => {
console.log('Error during the request:', error);
});

any suggestions?

the problem is not in the transfer but the truncated file is returned to me by the getraw api:

“await browser.messages.getRaw(messageid).then((messagey) => {…”

messagey is truncated (it would always seem to be 8KB) what could be giving me this limitation?

Please see ** READ THIS NOW - before posting. How to get help - the link https://thunderbird.topicbox.com/groups lists several groups which includes one for add-on developers to ask questions.