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Mobile Broadband

Problem with IMAP using mobile data

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4: Newbie

I've been trying to set up an email client to talk to my server using IMAP and have run into a problem. It all works fine when connected to my wifi but when using mobile data it fails with a certificate error. The certificate is fine.

 

This evening out of curiousity I set my phone up as a hot spot using mobile data and lo and behold my laptop can't connect to the server that way either (and yes, my router is appropriately configured, I've been running this server for nearly ten years now).

 

There is a curious difference between the two sessions recorded by my mail client. This is how the normal wifi session starts:

11/12/2018 18:20:45 S: * OK VPOP3 IMAP4rev1 Server
11/12/2018 18:20:45 S: TLS0 OK STARTTLS OK
11/12/2018 18:20:45 C: { ------ TImapLoginTask started ------
11/12/2018 18:20:45 C: 1 CAPABILITY
11/12/2018 18:20:45 S: * CAPABILITY IMAP4rev1 AUTH=CRAM-MD5 NAMESPACE ACL UIDPLUS ENABLE IDLE LIST-EXTENDED CHILDREN SPECIAL-USE CREATE-SPECIAL-USE METADATA
11/12/2018 18:20:45 S: 1 OK CAPABILITY completed

<Login command succeeds>

...

 

But here is how the session starts when using my phone as a hotspot and mobile data:

11/12/2018 18:18:26 S: * OK VPOP3 IMAP4rev1 Server
11/12/2018 18:18:26 S: TLS0 NO Error in IMAP command.
11/12/2018 18:18:26 C: { ------ TImapLoginTask started ------
11/12/2018 18:18:26 C: 1 CAPABILITY
11/12/2018 18:18:26 S: * CAPABILITY IMAP4rev1 AUTH=CRAM-MD5 NAMESPACE ACL UIDPLUS ENABLE IDLE LIST-EXTENDED CHILDREN SPECIAL-USE CREATE-SPECIAL-USE METADATA LOGINDISABLED
11/12/2018 18:18:26 S: 1 OK CAPABILITY completed

<Login command fails: STARTTLS required>

 

It looks to me like the STARTTLS command is being blocked/mangled when the connection is going via Vodafone mobile data.

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1 ACCEPTED SOLUTION

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4: Newbie

Oh, naughty Vodafone!

 

Having had my dinner I've spent a bit more time on this and if I modify things so that the Android app uses a different port it all works. So it appears that Vodafone are messing with traffic to port 143 to disable STARTTLS. Maybe it's an attempt to allow virus checking? I thought I'd turned off that safe networking thing - leastwise it says it's disabled in My Vodafone.

 

Much as I understand the thinking behind it I disapprove of ISPs that interfere with network traffic.

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1 REPLY
4: Newbie

Oh, naughty Vodafone!

 

Having had my dinner I've spent a bit more time on this and if I modify things so that the Android app uses a different port it all works. So it appears that Vodafone are messing with traffic to port 143 to disable STARTTLS. Maybe it's an attempt to allow virus checking? I thought I'd turned off that safe networking thing - leastwise it says it's disabled in My Vodafone.

 

Much as I understand the thinking behind it I disapprove of ISPs that interfere with network traffic.

View more options