Sometimes TB connects, sometimes it doesn't
For several months now, I have had a really strange problem. Most of the time, my email has worked properly, but occasionally it has played up – at those times I can send emails, but not pick them up. I have spent time on the phone with my ISP, and they found nothing. During the problem, I tried pinging the POP3 mail server from a command window – no response. And at the same time I tried pinging the SMTP (outgoing mail) server – all fine.
This problem has no other symptoms, and no other software seems to be affected.
I use a Belkin wireless modem / router, connected to the phone line (ADSL), and by Ethernet wire to my PC. For email I use Thunderbird. This setup has been the same for several years, except I got a new PC in autumn 2013, and there were no problems at that stage. The new PC uses Windows 7.
Sometimes re-starting Windows has fixed the problem – for a while – and sometimes it hasn’t. Switching the PC right off and on again gets things working properly, until the next time.
In the course of trying to fix this, I found this page (http://www.sevenforums.com/tutorials/94721-mtu-limit-test-change-your-connection-s-mtu-limit.html) and it started me wondering about the MTU settings. Full disclosure – I had never heard of MTU before.
In the PC, the MTU is set to 1500, as below. In the modem / router it is set to 1400. I didn’t set either of these myself. I don’t know if having two different settings like that is a problem. And looking at the sevenforums page, I wonder if I should reduce the 1500 to 1472. I hesitate to do that because I do not appear to be suffering packet loss.
Microsoft Windows [Version 6.1.7601] Copyright (c) 2009 Microsoft Corporation. All rights reserved.
C:\Users\Brian>netsh interface ipv4 show subinterfaces
MTU MediaSenseState Bytes In Bytes Out Interface
--------------- --------- --------- -------------
4294967295 1 0 343613 Loopback Pseudo-Interface 1
1500 1 28596266 2215303 Local Area Connection 1500 1 0 337019 Local Area Connection 2 1500 1 0 348593 VirtualBox Host-Only Network
A couple of months ago, I installed a VPN for the first time. I don’t routinely have the VPN on, because it’s free so I have limited bandwidth. I have found that, when the problem occurs, all I have to do is switch on the VPN, and I can collect email. Is this a clue? However, when I have the VPN on, it’s the other way round - I can collect mail, but not send it! Not only that, but TB often puts the message in the Sent folder, even though it has not been sent!
When I can't send an email, I get the message in the attached image.
I would appreciate any suggestions.
All Replies (7)
In the PC, the MTU is set to 1500 ... In the modem / router it is set to 1400.
That doesn't make sense. The MTU on your computer shouldn't be bigger than on your router. Why it's 1400 on the router, I don't know. If 1400 has been set by your provider, leave it alone. Then set the MTU on your computer to 1400 as well.
Thanks, I'll try that, and let you know in 2 or 3 days how it goes.
Well, that didn't work. I tried changing the MTU setting using the command
netsh interface ipv4 set subinterface "Local Area Connection" mtu=1400 store=persistent
But this is the result:
Microsoft Windows [Version 6.1.7601] Copyright (c) 2009 Microsoft Corporation. All rights reserved.
C:\Users\Brian>netsh interface ipv4 show subinterfaces
MTU MediaSenseState Bytes In Bytes Out Interface
--------------- --------- --------- -------------
4294967295 1 0 88620 Loopback Pseudo-Interface 1
1500 1 7776004 1629106 Local Area Connection 1500 1 0 74850 VirtualBox Host-Only Network 1500 1 6026874 870374 Local Area Connection* 11 1500 5 0 0 Local Area Connection* 12
C:\Users\Brian>
The attached image is of the settings on my router. I tried changing the router to 1454, but then I had no connectivity at all, instead of just TB having a problem.
I'd assume you need to have administrator privileges for this. In any case, for issues with changing the MTU you'd better ask in a Microsoft forum.
I tried changing the router to 1454, but then I had no connectivity at all
This is why I said leave it alone.
christ1 said
This is why I said leave it alone.
Point taken. I changed it back. But changing "Local Area Connection" to 1400 had no effect.
I tried pinging the POP3 mail server from a command window – no response. And at the same time I tried pinging the SMTP (outgoing mail) server – all fine.
Can you ping both, the POP and SMTP server now?
Yes, but that doesn't tell us very much. Half an hour ago, before lunch, I couldn't pick up mail. Now I can. In between, something happened by itself to change the situation.
I know, it doesn't provide very much to go on...