comcast.net Emails not being received

[lac21350]

I am responsible for sending bulk emails to my community. I use a web provider who processes my emails. I have 350 recipients and of those 123 are comcast.net email users. Recently not all emails that are being sent to comcast.net recipients are  making it into their inbox. The emails are NOT going to their Spam/Junk folder.  This is an intermittent problem. Recently I sent out 4 emails and I and many of my recipients only received 1 out of the 4. Some have received all of them. My web provider claims that all the emails went out and produced a picture of his log.  This is a serious problem because the community I am in is an older crowd and they depend on receiving emails about community events especially on snow emergencies. What can I do to resolve this serious problem?

[BruceW]

If @ComcastAntiSpam or another employee doesn't help you here, Comcast Security Assurance may be able to tell you what the problem is. You can reach them at 1-888-565-4329 (from https://internetsecurity.xfinity.com/help/report-abuse/). Note that this is NOT one of the general customer service numbers. The first-line reps there are sometimes not very helpful, so be persistent, and keep at them until you get a satisfactory resolution.

It would be good to have the name of the sending domain, and the name and IP address of the sending server ready to give them.