[SOLVED] Networking problems sending Telematik mails from VM

Jul 7, 2021
We have virtualized a medical information system on Proxmox running in Debian 9 Buster VM. Everything so far seems to work fine there is only an issue if we send data via a builtin account to contact the health services in a sort of email with attachment. To be precise we can message without a problem but as soon as the attachment gets a little bit bigger (still < 1MB) we receive tons of "out of order", "retransmission", "Dup ACK" errors on the interface. We already spend a lot of hours troubleshooting this and so far we can almost rule everything out but some networking issue in the VM or Proxmox.

Is there a recommended setting to have like the most robust network config, e. g.

- use e1000 or vmx3 instead of virtio?
- disable offloading?
- etc?

Any ideas or pointers are welcome!


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