email rejected on VPN

[DKS]

I am using ExpressVPN on my MacBook Pro, running macos 10.13.6 High Sierra. My email client Thunderbird 68.7.0 is no longer able to reliably send email while my VPN is running. Thunderbird puts my outgoing msg in the Outbox, but in fact the email was not sent. Instead I receive a pop-up msg which says the "The mail server sent an incorrect greeting: mtlp

[DKS]

Sorry. The pop-up error msg from Thunderbird says "The mail server sent an incorrect greeting: mtlp000083 cmsmtp Connection Rejected - see http://wwwspamhaus.org/query/ip/ ( my vpn-assigned ip  address). " I went to that web address and it indicated the address is linked to spam. If I change vpn servers, I get the same msg, but with a different ip address assigned to me by the new server. I do not send spam. I contacted ExpressVPN and their workarounds were no help. Their last suggestion was to bypass the vpn when using email, which is not a satisfactory solution. Neither is using Telus webmail, which does not cause me this problem. Why is Telus' email server treating my outgoing mail as spam? Are they trying to force all customers to use webmail?

[NFtoBC]

What SMTP settings are you using?

[DKS]

smtp.telus.net, port 587, no connection security

[FuzzyLogic]

Please verify that you are using the correct settings for Telus mail:

https://www.telus.com/en/bc/support/article/set-up-email-iphone-ipad

I don't believe that Telus uses Spamhaus (a blacklisting service) so it would appear to be an issue with your VPN provider. Spamhaus only blocks an IP address for 24 hours unless the address is reported again for spamming.

[DKS]

I'm not using an iphone or ipad...

[FuzzyLogic]

The settings should be the same regardless of the device/client you are using. Confirm the ports, SSL settings and server names.

[DKS]

I'm using IMAP for receiving, and its working fine, so those settings are good - imap.telus.net, SSL/TLS, normal password.

The SMTP settings are unchanged - smtp.telus.net, port 587, no connection security.

Thunderbird says the server is rejecting a connection. That implies the VPN is passing through the connection attempted by Thunderbird.

[Nighthawk · Accepted solution]

>> The SMTP settings are unchanged - smtp.telus.net, port 587, no connection security.

That is the entire problem in itself. You can only connect to smtp.telus.net without any connection security from a Telus IP. If you're using a VPN, you need to use the secure smtp settings to send. I've had no issues with Thunderbird on MacOS with the correct settings in it.

Server: smtp.telus.net

Port: 1025

Security: STARTTLS <<< Important. If SSL/TLS is selected, you will get a connection error. 

[DKS]

Problem has returned. I thought it was resolved on the 28th... I have not changed my configuration in the interim.

To recap, I am using Thunderbird on macos High Sierra, with ExpressVPN running. Thunderbird smtp config'd port 1025, connection security STARTTLS. When I send a msg, I receive this Alert msg from Thunderbird

"An error occurred while sending mail: The mail server sent an incorrect greeting: mtlp000087 cmsmtp Connection Rejected - see http://www.spamhaus.org//query/ip/(address assigned by ExpressVPN)"

The message is not sent.

If I disconnect from the VPN server, a test msg is accepted by Telus' server and received at destination.  When I reconnect to the VPN, I get the error msg.

[Nighthawk]

Some people have used VPNs to send spam. Sometimes their VPN servers / IP addresses get blacklisted.

[DKS]

That's not very informative, nor helpful. Some people who chew gum send spam. But not me!

Every IP that gets assigned to me by the VPN servers gets the same response, sooner or later. Telus or some 3rd party service engaged by Telus, is causing this. Talking to 1st level help desk is pointless. They don't even understand the problem. Last time I called the tech referred me to a pdf explaining how to configure the email client to work with gmail services. But Telus has never told me to switch. When I tried that setup, the connection was rejected because my account has yet to be shifted.

[Nighthawk]

Telus will not provide technical support for your VPN problems. Telus has no control over anything that happens with your VPN and they are not causing the problem with your VPN and inability to send email. When I use NordVPN, I am able to send email through Telus' servers with no problem, so the issue will be with your VPN provider.

ExpressVPN has only so many servers and hundreds of thousands of users if not more. The VPN provider is not assigning a single IP to you. You are connecting through a shared server with hundreds or thousands of other users. Some of them send spam. It may also depend heavily on which country the VPN server is in that you are trying to use as well.

The spam blacklists are external to ISPs and are shared. I would recommend reading through the Spamhaus website to learn more on what that service is and what it does. A huge number of companies use spam blacklist services like Spamhaus to deal with the enslaught of spam. VPNs are often targeted because they allow the spammers to rapidly shift between VPN servers when one becomes blocked.

[FuzzyLogic]

To add to what Nighthawk said an easy test would be to send message with the current configuration but NOT using your VPN service. If that works but the problem returns when you use your VPN that's a good indication that is where your problem lies. Note that Spamhaus blocks an IP address for 24 hours and then removes the block unless it's reported again. So you may find your VPN works one day and not the next.

[DKS]

The VPN is running when I use webmail, but the outgoing msgs are not rejected then, so it seems it's not the vpn. In any case, I've been using the same VPN for over a year, and the issue only cropped up recently.

With the VPN off, the IP is assigned by Telus, with VPN on, it's assigned by the VPN. Telus is blocking IPs assigned by the VPN. It has done the same thing to me when I was travelling outside Canada, even without the vpn running.

[FuzzyLogic]

When you use Webmail you are connected to the Telus servers for SMTP/IMAP/POP and thus don't have the issue. This is mentioned in the link I sent previously:

Note: Some countries may block these settings. If they are not working in the country you are in, you will have to use webmail.telus.net from any device.

You say you are using port 587 for SMTP. The link I sent says to use port 1025 and SSL. You will need to authenticate when connecting to that port (supply you Telus email credentials).

[NFtoBC]

Further to the comments of @FuzzyLogic , when you use your Telus assigned IP address, you are internal to Telus’ network, and can use an unsecured SMTP login on port 465 or 587, however, since your packets on VPN travel outside Telus’ secured network, you need to authenticate as though you were travelling internationally. Thus the link to the mobile device instructions, and port 1024 plus SSL.

[DKS]

What you say makes some sense. HOWEVER, the document does not say to use port 1024, BUT 1025, about which see my previous response to Fuzzylogic.

[NFtoBC]

Yeah, I mistyped 1024.

[DKS]

Setting smtp to port 1025 with SSL as you suggested put Thunderbird into a non-responsive state for about 6 hours. I had to shut down all applications before I could Force Quit Thunderbird, which macos rightly reported was Not Respnding. FYI.

[FuzzyLogic]

I found this information for configuring Thunderbird on a PC. Not sure how different it would be on a Mac:

https://www.telus.com/en/bc/support/article/set-up-telus-email-thunderbird-mozilla

It's interesting that the servers are now gmail. I know Telus is moving to gmail but I'm not sure if this is the case for everyone.