FWIW, when I lived in Seattle I found that Lumen's DSL service blocked it as well. It wasn't an obvious block, though. It was either some DPI or size-based fi

FWIW, when I lived in Seattle I found that Lumen's DSL service blocked it as well. It wasn't an obvious block, though. It was either some DPI or size-based filtering. I wrote it up here for posterity: https://blog.prolixium.com/2021/01/23/does-centurylink-dsl-block-sip/ https://blog.prolixium.com/2021/01/23/does-centurylink-dsl-b... It worked just fine through Comcast's Xfinity service (although at the time, that service had other critical issues for me..) and I have no problem now with Verizon Fios.