Email provider blocked

[#1]

I have email mailboxes provided by Heart Internet. Plusnet is blocking access to these. Why?

[#2]

AFAIK Plusnet do not block access to any other email services. I use two other email services myself without any issues.

What make you believe they are blocking access ? Could you explain what is happening when you try to access the mailboxes and we'll try and assist

[#3]

When connected via plusnet broadband over wifi, my email client cannot reach the email server. When I switch to the Vodafone LTE network the client can reach the server.

[#4]

Also, if connected via plusnet, the email server becomes reachable if I go through a VPN.

[#5]

From what I can see here https://www.heartinternet.uk/support/article/how-do-i-set-up-a-mailbox-using-imap-on-my-device-or-ma... the url for the Heart mail server is imap.extendcp.co.uk, is that correct ?

If it is, then can you post the results of a tracert to that address ?

Here's the results from my connection

C:\Users\xxx>tracert imap.extendcp.co.uk

Tracing route to imap.extendcp.co.uk [79.170.44.34]
over a maximum of 30 hops:

  1     2 ms     1 ms     1 ms  192.168.5.1
  2     8 ms     8 ms     8 ms  254.core.plus.net [195.166.130.254]
  3     8 ms     9 ms     9 ms  84.93.253.119
  4    10 ms     8 ms     8 ms  195.99.125.142
  5    10 ms    10 ms     9 ms  peer2-et3-1-5.slough.ukcore.bt.net [62.172.103.222]
  6     9 ms     9 ms     9 ms  195.99.126.187
  7    10 ms    10 ms     9 ms  siteprotect.security.neustar [68.142.82.89]
  8     *        *        *     Request timed out.
  9    16 ms    16 ms    16 ms  156.154.215.134
 10     *        *        *     Request timed out.
 11    16 ms    16 ms    15 ms  156.154.215.0
 12    41 ms    16 ms    16 ms  156.154.253.109
 13    16 ms    15 ms    15 ms  ae8.lon1-cr-sargas.bb.gdinf.net [188.121.32.69]
 14    21 ms    20 ms    19 ms  ae1-u100.lds1-pe-sirius.bb.gdinf.net [87.230.113.15]
 15    25 ms    22 ms    21 ms  ae0.100.sr-athena.lds1.dcnet-emea.godaddy.com [87.230.113.7]
 16    20 ms    20 ms    19 ms  mail34.extendcp.co.uk [79.170.44.34]

Trace complete.

[#6]

I'm on a phone. I don't have tracert.
The email client was actually set up to connect to mail.<my domain> but trying imap.extendcp.co.uk results in exactly the same behaviour. i.e. connection successful over plusnet + VPN or Vodafone LTE, connection fails over plusnet without VPN.

[#7]

Maybe the ports rather than address being blocked? They are 993 and 587.

[#8]

I've checked using all of the Plusnet DNS servers and they all resolve imap.extendcp.co.uk correctly so it doesnt look like a DNS problem.

i.e. connection successful over plusnet + VPN

If it works when using a VPN that would possibly imply that Heart are blocking access from your allocated IP.

Have you contacted Heart ?

Maybe the ports rather than address being blocked? They are 993 and 587. 

PN dont block any ports , I use two different email providers , both use ports 993 and 587.

[#9]

No but I guess that's the next step. Thanks for taking a look at it.

[#10]

Note that most email clients will try to send before collecting mail. So its likely that its the Heart smtp server that's rejecting the connection. TBH Ive never seen an imap server reject a connection based on IP.

[#11]

Some more information.

I've tested a connection using swaks (Swiss Army Knife for Smtp ) to what I believe is the Heart smtp server ( mta.extendcp.co.uk ) and I can at least connect and negotiate a TLS connection on port 587. Obviously I can go no further since I cant authenticate as I dont have an account

----------------------

swaks --server mta.extendcp.co.uk -port 587 --quit-after STARTTLS
=== Trying mta.extendcp.co.uk:587...
=== Connected to mta.extendcp.co.uk.
=== response in 0.038s
<-  220 mta3.hi.local ESMTP Exim 4.96 Sun, 28 May 2023 13:57:16 +0100
 -> EHLO ian-VirtualBox
=== response in 0.015s
<-  250-mta3.hi.local Hello ian-VirtualBox [80.229.xxx.xxx]
<-  250-SIZE 52428800
<-  250-8BITMIME
<-  250-PIPELINING
<-  250-PIPECONNECT
<-  250-AUTH PLAIN LOGIN
<-  250-CHUNKING
<-  250-STARTTLS
<-  250 HELP
 -> STARTTLS
=== response in 0.016s
<-  220 TLS go ahead
=== TLS started with cipher TLSv1.3:TLS_AES_256_GCM_SHA384:256
=== TLS no local certificate set
=== TLS peer DN="/CN=*.extendcp.co.uk"
 ~> QUIT
=== response in 0.014s
<~  221 mta3.hi.local closing connection
=== Connection closed with remote host.

[#12]

Router reboot fixed it. Don't know why I didn't think of that sooner.

[#13]

Possibly you got a different IP address allocated. Make a note of what IP you have now and if the problem returns, check if a different one has been allocated.