I am working in a quite restricted company. which is also blocking certain website categories. However mailcow is not blocked. I guess it depends on which categories are blocked.
If you know the blocklist provider and the specific blocklist, e.g. Sophos you can try to have your mailcow site exempt from that blocking list (with Sophos, not your IT department…)
That being said I found a way to bypass the firewall/proxy, I am using an SSH tunnel via companies https proxy, to reach my home infrastructure 😉