Thomson Routers from plusnet: problems using Gmail over wifi?


If you came to this page because of a Google search for this problem then here is my advice in a nutshell:

  1. Turn off the "Web Browsing Interception" feature in your router by setting it to "disabled".
  2. Set your wifi to b/g operation only to reduce data speeds - you probably don't need more than 54Mb/s if you are on ADSL
  3. Power the router off, count to 30 and power it back on.
  4. If the problem returns, repeat step 3.
  5. If the problem comes back frequently consider using a cheap timer plug to power cycle the router automatically in the middle of the night.

Oh, while you're here, could you just look at my PC?

Everyone who works in any job that is vaguely computer related will know that sometimes, when visiting a friend or relation's house the conversation will come around to some little problem they are having with their PC or home network. I had just such an experience at the weekend. I would normally have attempted to post the technical workaround to the plusnet forum where the particular issue I was debugging is being discussed but you have to be a plusnet customer to use the forums and I'm just a visiting techie so I'm posting what I know here.

The Symptoms

The scenario is a simple home network with a Thomson TG585 v8 ADSL router supplied by plusnet and an ordinary Dell laptop. I actually got a report of this problem earlier in the year. The main symptom was that email with attachments couldn't be sent. As the laptop owner spoke to me on a cordless wireless phone I could hear some interference on the line each time the laptop tried to send the email.

The First Diagnosis

This network is in a fairly isolated spot with only one other house within wifi range so interference from other wifi networks seemed unlikely. However, the house does have a cordless phone with a signal booster to reach to outbuildings. As is often the case with wifi issues you have to suspect interference, some older cordless phones are simply unusable alongside 2.4GHz routers. The obvious test is to instruct the user to plug their laptop directly in to one of the ethernet ports on the back of the router. Sure enough, the problem went away.

So is wifi really incompatible with this make of phone? The phone is of a modern design and is supposed to be compatible with wifi but perhaps that booster is the problem? To make the cable-based workaround easier the router was moved nearer the laptop. This took it further away from the phone and the booster - I had hoped that this might improve wifi connectivity enough for attachments to work but the problem remained. Needless to say, next time I visited the house the subject came up!

The problem gets worse

I must confess, I had forgotten about the problem completely until I arrived at the house and attempted to send an email via their wifi network from my own laptop. I was able to receive all my email no problem, web browsing was fast but I could not send messages through either my work email or through my Gmail account. Could this be related to the problem with sending attachments? Here is someone asking a similar question: Gmail, Windows Live Mail and Plusnet problems?

The problem appears so black-and-white I began to suspect that it must be a block at the ISP until I read this thread on plusnet's community forum: Mail cannot send attachments. The thread ends with an answer from a plusnet employee but the original problem from someone using Apple Mail (as I do) goes undiagnosed.

Eventually one of my smaller email messages managed to sneak out of my laptop at the Nth time of trying. Intermittent problems may be the worst to diagnose but at least this showed me that it is just a really bad connectivity problem.

I'm not alone

At this point I went back to my first diagnosis. I tried every channel, I powered off every other wireless device I could find (including the phones) and I still had the same trouble. This is beginning to look like a bug in the router. I checked the firmware version ( and found a new thread that matched my symptoms: Thomson TG585V8 poor upload speed over wifi and then the more general: Wireless connectivity on the Thomson V8. The second of these has 13 pages of discussion and brings the problem right up to date: but with no resolution!

The solution

To recap, we have a router that is perfectly capable of sending (downloading) data over wifi at high speed but is very bad at receiving it during uploads. I started suspecting some type of buffer overflow or error in one of the protocol stacks but restricting it to b or b/g operation didn't fix the issue either. I then started looking at other tools and settings in the router and came upon "Web Browsing Interception". I have no idea what this means but it was set to automatic. I found one post on a DSL forum which was enough to raise suspicion: Web Browsing Interception?. I disabled it and applied the settings, almost immediately my email started going through as normal.

The same feature is cited in this thread relating to different Thomson hardware (which I found later): "Solved: Thomson Speedtouch Modem, disconnects often and slows down browsing".

So did this solve the problem with attachments? No. At least not directly. Turning this setting off stopped the router interfering with mail clients making outbound connections to Gmail and Microsoft mail products. But I was still getting larger attachments stuck at about the 100Kb mark. It may be that all I have done is free up enough resource (RAM or CPU) to send small messages by turning off a feature of the router software. In which case, it seems likely that a resource leak of some kind is to blame in these routers. To test the theory I powered the router on and off, waited ages for it to restart (it really is slow) and then tried again. Everything worked fine - all attachments sending without error, even large ones.

So is this Web Browsing Interception feature to blame? Possibly, the router has been powered on and off before without fixing the problem so it seems likely that this feature is either causing or exacerbating a resource leak in the unit.