Tuesday, September 11, 2007

Comcast filtering Lotus Notes

For the past couple of months our Lotus Notes users (myself included) have experienced dropped connections in Lotus Notes when sending e-mail with attachments from a Comcast Internet connection. Evidently Comcast has implemented a filtering device to try and curtail the use of P2P software on it's network. Unfortunately they didn't do their homework and have applied this filter to port 1352 as well which is a registered Lotus Notes port.

Comcast won't admit to doing this even though there are posts about it all over the Internet.


IBM is writing a technote about it but they currently will not try to contact Comcast.

So if your Notes users are on a Comcast Internet connection and are trying to send an e-mail over 2 Mb thru a pass-thru server, they will get the pop up "Remote system no longer responding". Essentially the filtering device on the Comcast network sends a bunch of TCP RST packets back to the Notes client causing it to drop the connection. This is on uploads only, downloads work fine.


Andy said...

I feel your pain, because I am experiencing the exact same issue. I am in Philadephia region. It doesn't happen when I use Domino Web Access and upload a file, just with Notes. It started I think in the July/August timeframe when I was emailing large powerpoint presentations.

- Andy Pedisich

Kevin Kanarski said...

Hi Andy,

It looks like we are going to provide IBM some more network traces and maybe they will talk to Comcast.


Jim Knight said...

Thanks for posting this. This issue drove me nuts the last month or so with 2 client users working from home. We had them sending via iNotes but it was baffling to us what the problem was. We blamed it on a slow/dropped connection but now I know better and 2 MB was about the threshold I recall. They are in NJ.

Chris Whisonant said...

I will have to test this out. I'm on Comcast here in GA. I have never noticed it. Does it just happen if you're going through a passthru server or if it's a direct connection too?

Welcome - you've been Brilled; enjoy the traffic... :)

Andy said...

It breaks using direct connect for me.

- Andy Pedisich

Kevin Kanarski said...

I'm hitting a pass-thru server but any 1352 traffic will get filtered.

Thanks Chris. You talked me into starting a blog and look what happend ;)


Anonymous said...

Thanks, I'm having the same issues here in Chicago with Lotus Notes email and Comcast. I've called Comcast and raised a trouble ticket.

Wayne said...

Has any progress been made with this? Our office in Griffith, Indiana seems to be having this exact issue. I'm on hold with Comcast right now.

Anonymous said...

I don't know if this is related but I support a company that uses Lotsu Notes. They have a buisness class connection but I have had several complaints of them not being able to send outbound email to @comcast, everything gets kicked back with the following message.

Error transferring to gateway-s.COMCAST.NET; SMTP Protocol Returned a
Permanent Error 550 blocked by
ldap:ou=rblmx,dc=comcast,dc=net -> BL004 Blocked for spam. Please see

The ip is certainly not on any blacklist. So I assume this is related to the discussion, but I am a developer and not an admin so my speculation stops here.

Timothy said...

Are these home or business Comcast accounts? I am switching our Notes from DSL to Comcast. I was able to move 40mb files between the DSL and Comcast lines with no trouble.

Kevin Kanarski said...

My testing was done with a Comcast standard home account but someone else on a Comcast Business account had the same issue.

As my most recent post states it seems to have cleared up for now. I don't have an issue in Chicago and Andy from the comment above reported no issues as of this weekend on his blog.