sorry for the late reply. To be honest, I haven't tried Monarco HAT with PoE HAT. However, by specification, HAT devices are not generally stackable. Monarco HAT should be powered by 10-30 VDC. PoE HAT supplies only 5 VDC. So I don't think it will work.
@mtomek Hi Michal,
thank you for sharing your findings with the community.
Google uses more secure version of TLS which does not support the SMTP function block. Seznam apparently didn't upgrade the security yet.