Error - File is over 15mb, this might cause reduced performance.
Problem reported by Chew Man Fai - 8/18/2025 at 8:30 PM
Submitted

Hi,

We are experiencing slowness when accessing webmail. There is no issue observed from the server side, as it appears to be running smoothly. However, from the SmarterMail logs, we found the following errors:

[2025.08.19] 00:04:23.183 [FileFunctions] File is over 15mb, this might cause reduced performance. Size: 16.5mb Filepath: F:\SmarterMail\Domains\se***\Users\ray\folder-80003.json
[2025.08.19] 00:05:28.201 [FileFunctions] File is over 15mb, this might cause reduced performance. Size: 37.2mb Filepath: F:\SmarterMail\Domains\mit***\Users\mm\folder-720003.json
[2025.08.19] 00:05:32.389 [FileFunctions] File is over 15mb, this might cause reduced performance. Size: 25.8mb Filepath: F:\SmarterMail\Domains\mit***\Users\ro\folder-870003.json
[2025.08.19] 00:05:35.826 [FileFunctions] File is over 15mb, this might cause reduced performance. Size: 32.9mb Filepath: F:\SmarterMail\Domains\mit***\Users\to\folder-970003.json
[2025.08.19] 00:05:39.733 [FileFunctions] File is over 15mb, this might cause reduced performance. Size: 33.3mb Filepath: F:\SmarterMail\Domains\mit***\Users\wan\folder-980003.json
[2025.08.19] 00:05:46.592 [FileFunctions] File is over 15mb, this might cause reduced performance. Size: 20.2mb Filepath: F:\SmarterMail\Domains\mit***\Users\yutaka\folder-7830003.json

Could this be the root cause? Previously, we tried renaming the affected .json files, and performance improved temporarily, but the file sizes eventually exceeded 15MB again.

Do you have any suggestions to resolve this issue permanently? Would upgrading to the latest version help address this problem?

Thank you.

Derek Curtis Replied
Employee Post
If the users with those folders are the ones experiencing issues, then yes, that may be the issue. Did this just start occurring? Did you recently upgrade the server?

Looking at your account, you have a number of different licenses across various versions. Just want to try to narrow down which version is seeing the issues.

As an aside, renaming JSON files is not generally recommended as it can lead to other issues. 
Derek Curtis COO SmarterTools Inc. www.smartertools.com
Chew Man Fai Replied

Hi Derek,

This issue is occurring under version Build 8587. We have not upgraded the server yet.

Yes, we are using different licenses across various versions, and the usage for each license can be considered the same. So far, this is the only instance experiencing the issue.

Nageswara Rao Anumolu Replied
We are facing same issue with one of the domains where user count is 20,000. It takes 15 secs to load user inbox every time.
Kyle Kerst Replied
Employee Post
Just a quick tip that may help here. You can mitigate the performance impact of large user's JSON files in most cases by improving disk performance. If you have enterprise SSD/NVME/etc hardware it should minimize the impact of those users on other users of the same server significantly. 
Kyle Kerst Acting IT Manager SmarterTools Inc. www.smartertools.com
Zach Sylvester Replied
Employee Post

Another option you can try is adjusting the Config File Cache size. Go to Settings → Troubleshooting, then change the cache size from Automatic to 3 GB or 4 GB, depending on the memory available on your server.

This won’t reduce the initial load time, but it allows more objects to be stored in memory. If many users are logged in at the same time, this can help improve performance since the system won’t need to read from disk as often.

Keep in mind this is just a suggestion and not a guaranteed fix, but it’s worth testing. Please let me know if it makes a difference.

Zach Sylvester Software Developer SmarterTools Inc. www.smartertools.com
Nageswara Rao Anumolu Replied
There seems to be a caching and or data handling problem with contacts.

When ever the users clicks new, the contacts data loading again and again which is causing delay of 15 to 30 secs for each mail. There is nothing to do with the server configuration.

I am running AWS r6a.24xLarge (96 cpus, 768Gb Ram), EBS volume IO2 44tb 1,28,000 IOPS. Checked with reducing the IOPS to 32,000. There is no gain/loss  with the change in IOPs on the performance.

Nageswara Rao Anumolu Replied
We hosted 50 domains on the same server and on the same drive. This problem is with one and only domain with an user base of 20,000.
Zach Sylvester Replied
Employee Post
Hello,

Thank for for those details. I will talk to the team on monday and do some testing. 

Kind Regards,
Zach Sylvester Software Developer SmarterTools Inc. www.smartertools.com
Zach Sylvester Replied
Employee Post
Hey Nageswara, 

I discussed this with my team and we are looking into ways to make this better.  

Kind Regards, 
Zach Sylvester Software Developer SmarterTools Inc. www.smartertools.com
Nageswara Rao Anumolu Replied
Any update?
Zach Sylvester Replied
Employee Post

Hey Nageswara,

We’ve made improvements to help the email and mail pages open faster and run more smoothly. Contacts now load in the background, so the page won’t freeze up when you’re sending an email. The only time you may notice a short delay is if you click the To: field before the contacts are fully loaded. Otherwise, the page will stay quick and responsive.

We also updated the Mail page itself so it loads faster overall.

As for caching, we chose not to store contacts long term in the browser. That approach can lead to outdated information and adds unnecessary complexity. By loading contacts fresh each time, we make sure the information you see is always accurate and up to date, while still giving you better performance.
These improvments will be in the next release.

Kind Regards,

Zach Sylvester Software Developer SmarterTools Inc. www.smartertools.com
Nageswara Rao Anumolu Replied
Is it possible to share the build?
Zach Sylvester Replied
Employee Post
Hey Nageswara, 

This was in our last release. Let me know if you see any improvement. 

Kind Regards, 
Zach Sylvester Software Developer SmarterTools Inc. www.smartertools.com

Reply to Thread

Enter the verification text