Unable to access SMTP servers only when connected to MWeb's network?

[LoganY87]

I have a 2mbps ADSL connection with MWeb on a new account and separately, I got a free 1GB capped account with Axxess some time ago.

When connected to MWeb's network, I'm not able to connect to any SMTP server via Outlook or telnet. That is to say, any SMTP server, except MWeb's.
I can, however, connect to any SMTP server when I'm connected using my Axxess account.

MWeb have assured me that they're not blocking anything to do with email but the fact remains I can't use my SMTP server when connected to their network.

An attempt to telnet into vodamail's SMTP server (solely to test the connection) yields the following:

Microsoft Telnet> open smtp.vodamail.co.za 25
Connecting to smtp.vodamail.co.za...

421 Cannot connect to SMTP server 196.11.146.149 <196.11.146.149:25>, NB connect error 1460

Connection to host lost.

Press any key to continue...

I would be happy to substitute MWeb's SMTP server in my mail setup, however, there are problems with that to do with SMTP relays I believe. See below:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:

[email protected]
SMTP error from remote mail server after end of data:
host mail.ucebox.co.za [197.242.152.131]: 550 196.35.198.21 is not allowed to send mail from loganyoung.za.net.

In this case, I tried sending an email to Afrihost from my business email account which should use mail.loganyoung.za.net as the SMTP server, but I was using MWeb's SMTP server at the time given that I couldn't connect to my own.

I'm very confused about all of this and I've submitted a support request 18 hours ago under [REF# 20160405008826] but have yet to receive any response.

Since this problem seems to be specific to MWeb's network (a conclusion I've arrived at since everything works perfectly fine when I'm connected to Axxess' network), I think I might have to cancel my account with MWeb and move my service to another ISP...

 

[drs]

From the evidence you've shown, M-Web are certainly blocking outgoing connections to port 25. They ought to do that, to prevent their users originating spam; though they ought to tell you that when you ask.

RFC 5068 section 3.1 requires that e-mail operators support authenticated e-mail submission on port 587 if they permit e-mail to be originated from outside their network. mail.vodamail.co.za does not accept connections on port 587. Either Vodacom don't intend for you to submit mail from outside their network, or they're out of compliance with the RFC. Either way, get a better e-mail provider.

mail.loganyoung.za.net does accept connections on port 587. Try setting your mail client to use port 587 and enable authentication.

 

[The_Librarian]

Mweb do block outgoing port 25 to prevent spam. As do most ISP's.

Port 25 is only open to that specific ISP's email servers.

Only way around that is to get a static IP...

 

[AstroTurf]

Mweb have a external smtp server thing you should ask them for.

 

[LoganY87]

From the evidence you've shown, M-Web are certainly blocking outgoing connections to port 25. They ought to do that, to prevent their users originating spam; though they ought to tell you that when you ask.

RFC 5068 section 3.1 requires that e-mail operators support authenticated e-mail submission on port 587 if they permit e-mail to be originated from outside their network. mail.vodamail.co.za does not accept connections on port 587. Either Vodacom don't intend for you to submit mail from outside their network, or they're out of compliance with the RFC. Either way, get a better e-mail provider.

mail.loganyoung.za.net does accept connections on port 587. Try setting your mail client to use port 587 and enable authentication.

Thanks, that's very informative so far I haven't had any problems sending email from my vodamail account so I'm not too fussed about not using their SMTP server, but now I see I can connect to mail.loganyoung.za.net on 587 so that ought to fix the SFP problem I was getting.

Now I have new problems, however.

Connecting to mail.loganyoung.za.net on port 587 has confused the issue.
If I don't use authentication, Outlook tells me to verify my email address but if I do use authentication, Outlook tells me that none of the authentication methods supported by my client are supported by the server...

I specified Encryption method of Auto and that fixed the problem using auth.

 

[drs]

Connecting to mail.loganyoung.za.net on port 587 has confused the issue.
If I don't use authentication, Outlook tells me to verify my email address but if I do use authentication, Outlook tells me that none of the authentication methods supported by my client are supported by the server...

Check that you have TLS enabled. mail.loganyoung.za.net:587 only supports authentication after STARTTLS, so that your password is not sent unencrypted.

$ openssl s_client -quiet -connect mail.loganyoung.za.net:587 -starttls smtp
depth=0 C = US, ST = Virginia, L = Herndon, O = Parallels, OU = Parallels Panel, CN = Parallels Panel, emailAddress = [email protected]
verify error:num=18:self signed certificate
verify return:1
depth=0 C = US, ST = Virginia, L = Herndon, O = Parallels, OU = Parallels Panel, CN = Parallels Panel, emailAddress = [email protected]
verify error:num=10:certificate has expired
notAfter=Mar 13 13:29:18 2016 GMT
verify return:1
depth=0 C = US, ST = Virginia, L = Herndon, O = Parallels, OU = Parallels Panel, CN = Parallels Panel, emailAddress = [email protected]
notAfter=Mar 13 13:29:18 2016 GMT
verify return:1
250 DSN
EHLO foo.bar
250-apollo.radiantnet.co.za
250-PIPELINING
250-SIZE 10240000
250-ETRN
[b]250-AUTH PLAIN CRAM-MD5 LOGIN DIGEST-MD5[/b]
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN

If that doesn't work, get in touch with whoever operates the server.

 

[fragtion]

Mweb (like other ISP's such as Vodacom as well) do a NAT intercept on SMTP traffic, forwarding the traffic to their own SMTP relays instead, whenever the following two conditions are met:

1) Your destination SMTP server hostname as specified, starts with smtp.*
2) Outgoing traffic to that target server is made on port 25

There are two solutions I have found if you want to bypass this behaviour:

1) Use the static IP address for your chosen SMTP server instead of the smtp.* hostname
2) Use an alternative port for the SMTP server, usually such as port 587