Tired of your emails not reaching their destination? Hitting the send button only to find your messages and IP is blocked by ISPs can be frustrating. If you’ve been struggling with your email campaigns or SMTP server having pending sending issue, you’re in the right place. This post, Troubleshoot and Fix Email Deliverability Issues, will walk you through a real-life case study of a client who faced a very critical delivery issues with postal smtp server. I believe this will help you understand common problems and, more importantly, how to solve them. By the end of this guide, you’ll be well-equipped to troubleshoot and fix email deliverability issues, ensuring your emails consistently land in inboxes, not spam folders irrespective of the mail transfer agent you are using. Let’s dive in.
I have written two different guides on how to set up SMTP server and send unlimited emails with postal smtp and another with mailinabox. You can check them out to see the different options to build smtp server.
I also have a udemy course on how to build a fully-featured cold mail outreach system and send unlimited emails. You can check it out too as I really dived deep into the technical side of email marketing.
Fixing Postal Pending sending Issue.
Now let’s see how to Troubleshoot and Fix Email Deliverability Issues with postal smtp. I will like you to have this understanding that thing are pretty similar irrespective of the mail transfer agent you are working with. But, this specific issues happend with postal and this was the process I took to troubleshoot and fix things up.
The first thing I did to address the slow sending was to check his server specifications, and I found that his VPS architecture consists of 1 vCore, 1 GB RAM/40 GB SSD NVMe. Given the high volume of emails he sends within a short period, this configuration is likely to cause issues with crashes. I upgraded the server and adjusted some important postal settings to keep the server load within an optimal threshold. For the upgrade moved from his provider to Contabo because they offer Solid and way bigger server resources at affordable price. So, if you are building an smtp server, I recommend you go with Contabo as they open port 25 by default, and they also offer huge server architecture and a very affordable price.
Adjustment of default postal settings
After the server upgrade, the next thing I did to Troubleshoot and Fix Email Deliverability Issues is to adjust some default postal settings to fit the client’s need.
I set the Message retention days to 0, Raw message retention days to 0, and the Raw message retention size to a maximum value of 1 MB. These values ensure the message headers and contents are not over-accumulated on the server, keeping its size <= 1mb.
Then, for the pending sending issues, I found out that Postal SMTP servers can implement automatic throttling to manage the flow of messages, especially for new servers. This often involves rate limits to prevent abuse or overwhelming the server. Examples of throttling limits include messages per minute and recipients per day. The system can also release held messages when the message count falls below the maximum limit, optimizing email delivery. So I modified this numerical value to a high value in the postal config file, and that fixed the pending sending issues.
IP Block fixes
There comes another issue of IP blocking. I noticed that the primary sending IP and the four outbound IPs associated with this primary IP have all been blacklisted. So we’ve got to get them off the blacklists. I used MXToolbox and Spamhaus to detect and remove the IP ranges from the blacklist. So by doing these, I was able to get the server clean and up and running again.
To detect your server IP or domain from the major blacklist, input your domain or IP in the field as in the screenshot below and you will see the blacklists you are in. Do same for spamhaus and you will see the guideline to remove them. Just follow the prompt and and you will be able to remove it.
My Advice to senders
My advice to the client to avoid getting his server blacklisted again: Just like I said before, he sent out a lot of emails immediately after setup. When you have a new server set up, you don’t send out a lot of emails because this is a new IP with a zero reputation. You’ve got to build trust and reputation by sending a small volume and subsequently ramping up volume over time.
Secondly, I made sure he validated his email list before continuing the send again. A close look at the screenshot in this post, you will notice that his server bounce rate is over 30%, meaning he is sending to a lot of non-existent emails or catch-all, which is ridiculous.
Lastly, I ensured he set up a bounce server to handle future bounce emails and auto-remove them from the sending list.
NOTE: This is not all there is to troubleshooting email deliverability issues. Your case will depend on your MTA’s error log analysis. If you are having email deliverability issues or your case is peculiar, you can reach out to me to analyze and fix your scenario.