Of cPanel updates and email connection limitations.

Written by Tyler Jacobson on December 6, 2012

Fortunately, only a few of our servers yesterday were negatively effected by a cPanel update that reset our email connection limits.

Unfortunately, a few of our servers yesterday were negatively effected by a cPanel update that reset our email connection limits.

Now, we don’t want to blame cPanel. They offer a robust product and these updates were essential to closing a security gap before it was exploited. This is what good and responsible developers do and we appreciate their attention to addressing potential issues. (We hope that, as a MacHighway customer, you also appreciate that your server isn’t compromised due to a vulnerability.)

Under most circumstances, a reset of the mail connections limit would go unnoticed by an end user. In a traditional scenario, your email client will open a connection, send or receive email, and then close the connection, thus freeing it up for the next party who needs to send or receive….

…but we’re Mac users and our needs are different. In most cases, that’s a good thing. In this case, it’s not.

Apple has created Apple’s Mail app in a ponderously special way (we suspect it’s in a way that is particularly beneficial to .Mac/MobileMe/iCloud.) When you have Apple’s Mail app setup to check via an IMAP connection, it opens up to 6 connections to the server per email account and then keeps those connections open as long as the Mail app is open. In other words, it won’t free up those connections to the next user who is sending or receiving their mail. It locks those connections up whether it needs to or not. For every additional account you check via IMAP in Apple’s Mail app, the problem is only amplified.

Even if you don’t use Apple’s Mail app you’re affected by this, unfortunately, since many of your fellow users on the server do use Apple’s Mail app. Each time one of them opens up their Mail app, more available connections from the shared pool are used for an extended period of time.

To compensate for this, we raise the maximum mail connections to a much greater higher threshold so that this limitation goes unnoticed by you, our customer. I’m happy to report that it works once that limit is raised, however, when that limit is reset to it’s default…. let’s just say that no one is happy until it gets adjusted.

This maxed out limit then presents a new problem, as customers are now anxiously waiting for their email to become available again. So, we raise the limit, but now we have double or triple the amount of people attempting to receive their email all at the same time. To satisfy that demand we must keep raising the connection limits, but still, we may find our available connections maxed out. This will continue until the peak hours of usage are over and fewer people are requiring an immediate response from the email server.

I’m happy to say that as of our peak hours today that things appear to be working and email is being sent and received without an issue.

Q: “So, then, why don’t you just allow infinite mail connections?”

A: Good question.¬†Running a shared email and web hosting server is a constant balancing act. Every increase in the maximum mail connection limit comes with a cost of CPU and disk access overhead. If we raise the limit too much, the server will slow down in serving up pages, delivering your email, sending your email, etc. …. all processes will suffer. We both load balance our servers and adjust connection limits so as to not sacrifice a high quality hosting experience. We do our best to make sure that all of our services are fast and reliable.

Q: “Why are you blaming Apple? I thought you were Mac friendly.”

A: Another good question. Our interest is in getting the problem solved. We do everything within our power to rectify problems once they come up. This is why we raise these limits, such as the maximum mail connection limit, because we know that issues like this exist with the Mail app and that you would rather not have a roadblock to getting work done. What we can’t do is change the way Apple’s program works.

Believe me, we’ve tried.

I have, personally, contacted Apple about this on multiple occasions, attempting to speak to a developer so we could illustrate the problem that this presents, not only for MacHighway, but every email host who has customers using their Mail product. Since we’re the world’s largest Mac specific host, we tend to notice these issue much more than other hosts that don’t specialize in Mac hosting. As of yet, we haven’t been able to connect with anyone who is in a position to investigate and resolve this issue. If you know of anyone, please tell them to get in touch with us.

I, like many of you, use Apple’s Mail application and I find it quite useful. I’m a fan. But, it’s important to recognize that this is a unique circumstance that using this specific application presents and we wish Apple would fix it.

Q: “Is it true that I can just uncheck ‘Use IDLE command if server supports it’ under preferences and this issue of connection limits goes away?”

A: We wish this were the case. We’ve done extensive testing and, unfortunately, toggling that box doesn’t appear to have any effect on the number of connections to the server or the dropping the connections. We’re not sure if Apple believes that it has an effect or not. For anyone from Apple who may be reading this, we’d be more than happy to troubleshoot this with you. We’d jump at the opportunity.

Q: “How do you make sure this doesn’t happen again?”

A: You pull no punches in your questions and I appreciate your directness. Unfortunately, I can’t assure you that this won’t happen again as it’s very possible that this very same issue may present itself again.

What I can assure you of is that if it does happen again, we will do our best to resolve the issue as quickly as possible. It is in our best interest to have your sites and email running problem free. We will do our best to earn your confidence and make hosting with us easy and fuss free.