Tiger,
Colossians is one of the letters that is considered was not written by Paul.
Only 7 of the NT missives attributed to him are considered to be genuinely by him. And of those which are, some are compilations of several letters and some are missing (Laodicea, for example).
For the first two centuries, only "heretics" such as Marcion (mid-2nd century) used Paul's writings but the church fathers did not oppose him by quoting Paul's writings. At that stage, the church considered Paul's writings were not catholic (for the church as a whole) because they were written to a particular church over a specific incident.
Doug