I am using imapsync to copy messages from ProtonMail to Zoho. The messages are all downloaded on my computer via ProtonMailBridge but they're being uploaded to Zoho at a dismal speed -  12 KiB/s at the moment. I have a high speed optical internet 80 MiB/s and currently there is no other network activity to interfere with this. The ETA for less than 2GB is 16h. Yesterday I uploaded 4 GB file to filen.io for less than 10 minutes. What's wrong?