SMTP gateway with networking

[Mage]

I’m setting up an SMTP server in a cloud (Google) where email ports are blocked (outgoing traffic for sure, maybe both). Normally, I’d set up a smart host at another provider on a custom port. It works, but considering the number of emails to send and the budget of the project, I can’t justify the cost.

Since all I need is an IP address that allows traffic on SMTP port, a network-based solution would cost ten times less than a smart host. The idea is that:

1. When the SMTP server sends an email, it connects to the external server on a custom port. The external server connects the destination host.
2. The incoming SMTP connections go to the external server that forwards them to the SMTP server on a custom port (or another way).

I’m not a network expert but I’m also not asking for a detailed guide. Initial hints would be great. Should I go for VPN or port forwarding (in both directions) or something else?

 

[obsigna]

I suggest to go for the SMTP relay method.

Sending email from an instance | Compute Engine Documentation | Google Cloud

Discover how to send mail from a VM instance using standard email ports and recommendations on third party emails & setting up email firewall rules.

cloud.google.com

I use AWS-EC2 instances which got the outgoing SMTP port open, however, some peers do block e-mails comming from the AWS networks, and therefore I use the mail service of my domain hoster for relaying mails to some specific destinations.

 

[Lamia]

Just as Obsigna said, you can rely on an SMTP relay for the naughty providers that won't accept emails from your IP address or domain. That is for the outbound email.
For inbound emails, there is little to worry about so long your server is well configured and that includes DANE/DMARC and firewall. Make sure your IP address isn't burnt for being a spam relay.

 

[Mage]

Just as Obsigna said, you can rely on an SMTP relay for the naughty providers

No, I can’t. Otherwise. I would not open a thread.

 

[Mage]

I suggest to go for the SMTP relay method.

Sending email from an instance | Compute Engine Documentation | Google Cloud

Discover how to send mail from a VM instance using standard email ports and recommendations on third party emails & setting up email firewall rules.

cloud.google.com

I use AWS-EC2 instances which got the outgoing SMTP port open, however, some peers do block e-mails coming from the AWS networks, and therefore I use the mail service of my domain hoster for relaying mails to some specific destinations.

If I ask a question on a forum and don’t describe the issue I’m trying to solve then people tell me to describe the issue. I can understand that.

When I describe the issue, I’m usually offered those solutions that I already excluded in the OP.

I opened the thread in the network section (instead of, for example, the business section) because I believe that there are network-based solutions that could be helpful for others too who run into a similar problem one day. It seems I have to figure it out alone.

Most likely it will be VPN since I also wanted to eliminate the SSL overhead between the internal server and a smart host in another project.

By the way, one of the providers recommended by Google would cost me about $20,000 per month for all my sites. That’s what I expected. Other providers would cost similar. An SSD VPS server costs $5 per month.

 

[obsigna]

If I ask a question on a forum and don’t describe the issue I’m trying to solve then people tell me to describe the issue. I can understand that.

When I describe the issue, I’m usually offered those solutions that I already excluded in the OP.

I opened the thread in the network section (instead of, for example, the business section) because I believe that there are network-based solutions that could be helpful for others too who run into a similar problem one day. It seems I have to figure it out alone.

Most likely it will be VPN since I also wanted to eliminate the SSL overhead between the internal server and a smart host in another project.

By the way, one of the providers recommended by Google would cost me about $20,000 per month for all my sites. That’s what I expected. Other providers would cost similar. An SSD VPS server costs $5 per month.

I deleted my answer already. Good luck with your Spam business.