I had a rock solid instance of IncrediblePBX going until a few months ago when all email from both the voicemails and from AvantFax just stopped arriving. It was a basic install on a Raspberry Pi. Thinking I screwed something up or the SD card got corrupted, I decided to try a fresh install on a different machine, however I had the same problem on the new install so I decided to dig a little deeper. I tried sending a test email from the command line with sendmail and discovered that my ISP (Comcast) is rejecting my mail because it's coming from an invalid domain. "reason: 550 5.1.0 <firstname.lastname@example.org> sender rejected : invalid sender domain" I read through a bunch of posts on this forum, some from 2008, some newer, and tried changing a lot of settings but never got it sorted out. Some of the suggestions relied on files that have changed names or moved locations. I've reached the point of asking for help. I tested with telnet to see if port 25 is blocked, it is not. I changed /etc/mail/sendmail.cf to include comcast (DSsmtp.comcast.net), no luck, and no change to the error message. I edited my hosts file and, voicemail.conf, no change. It seems like there is something simple I missed here and I can't understand why it used to work on my old machine and then just stopped. Can anyone give an up to date guide for setting up email from a stock install? My details are IncrediblePBX13-13.iso running in a VM on Proxmox on a NUC. I have a 3CX install in another VM and it sends emails just fine. Thanks!