We have just setup a fax machine using an HT287. When we send faxes a lot of the machines come back with Dirty Line errors and the fax is not sent. There is 1 fax that we send to which is built into a photo copier at a large office and do not get the line error. We use NexVortex for our provider. Grandstream: Software Version: Program-- 126.96.36.199 Bootloader-- 188.8.131.52 HTML-- 184.108.40.206 VOC-- 220.127.116.11 Can anyone shed some light on tweaks I may need to make to the 267 - or perhaps another adapter I should be instead using... Thank you in advance.