Nextcloud Mail Slow? Learn How to Speed It Up

No doubt, Nextcloud Mail is quick, but sometimes in many setups, the inbox takes too long to load, and folders lag. The root cause is rarely the email provider. It mainly occurs due to IMAP authentication failed, or sync issues, and stores metadata in the database. 

Whatever the reason, it doesn’t matter; how to fix it is now the challenge. Today, in this discussion, I’ll share all the possible troubleshooting fixes which easily resolve this error in minutes. So, let’s start this discussion with how it appears!

How the Problem Usually Appears

Before moving to the fixes, first let me explain when the Mail app is slow. I observe:

• Inbox takes minutes to open
• Emails load one by one instead of all at once
• UI freezes while switching folders
• IMAP server timeout
• Nextcloud logs show background job delays

This is not a normal behaviour. Properly configured, the Nextcloud Mail app is responsive. If you’re facing the same, then next we’ll discuss why it occurs.

Why is Nextcloud Mail Slow

Knowing the causes behind Nextcloud Mail slowness is necessary to prevent this in future. So, don’t skip this section.

Nextcloud Mail feels slow because it does more work in the background than a normal email client. Instead of just showing emails from the IMAP server:

• It keeps syncing message details.
• Storing metadata in the Nextcloud database.
• Checking the mailbox status again and again.

All this extra work makes Nextcloud Mail slow when the server is not tuned properly.

In simple terms, Outlook or Thunderbird just shows emails directly from the mail server, but Nextcloud Mail does extra work before showing emails.

Before you see your inbox, Nextcloud:

• Configure with the IMAP server
• Downloads email details
• Stores those details in its own database
• Checks old records
• Updates the message status
• Handles background sync tasks

All this happens every time you open Mail.

If the server is not powerful or not configured properly, this extra work makes it slow. Here are some more reasons:

• With a large dataset, more emails to check and store
• Weak database settings enhance the inbox time to load
• Too many folders/labels to sync
• Low memory leads to slow processing
• Big mail cache tables mean slow database reading

So the slowness is not because of your email provider; there are numerous factors behind that.

Here’s How to Resolve Nextcloud Mail Slow Step by Step

Below are all the practical fixes to troubleshoot this issue permanently, so don’t skip any of them, as all are crucial:

Fix 1. Enable System Cron (Not AJAX)

• In Nextcloud, click on Settings.
• Then, select the Basic Settings > Background Jobs.
• Lastly, hit the Cron option.

Then on the server:

crontab -u www-data -e

Add:

*/5 * * * * php -f /var/www/nextcloud/cron.php

#Fix 2. Configure Redis

Install Redis:

apt install redis-server php-redis

In config.php:

‘memcache.local’ => ‘\\OC\\Memcache\\Redis’,

‘memcache.locking’ => ‘\\OC\\Memcache\\Redis’,

‘redis’ => [

   ‘host’ => ‘localhost’,

   ‘port’ => 6379,

],

Restart services.

#Fix 3. Increase PHP Limits

In php.ini:

memory_limit = 1024M

max_execution_time = 360

#Fix 4. Tune MySQL / MariaDB (Critical)

Add to my.cnf:

innodb_buffer_pool_size = 2G

innodb_log_file_size = 512M

innodb_flush_log_at_trx_commit = 2

max_connections = 200

Restart MySQL

#Fix 5. Enable APCu for Local Cache

apt install php-apcu

In config.php:

‘memcache.local’ => ‘\\OC\\Memcache\\APCu’,

#Fix 6. Reduce Mailbox Sync Load

In Mail app settings:

• Disable Show avatars
• Disable Threading
• Reduce Messages per page
• Remove unused accounts

#Fix 7. Clean Mail Cache Tables

Do this when mail is already very slow:

TRUNCATE oc_mail_messages;

TRUNCATE oc_mail_recipients;

TRUNCATE oc_mail_attachments;

Now, Nextcloud will rebuild the cache fresh and faster. The Nextcloud Mail slow issue is resolved.

#Fix 8. Increase IMAP Timeout

In config.php:

‘mail_smtptimeout’ => 60,

#Fix 9. Upgrade Nextcloud and Mail App

Older versions of the Mail app had performance bugs. Always update to ensure a smooth configuration. 

After applying these fixes, you will see the result in minutes, like:

• Inbox will load in seconds
• Smooth navigation
• Low server load

When Nextcloud Mail Will Still Be Slow

Even after implementing the discussed troubleshooting steps, it will be slow if:

• Mailbox has 50,000+ emails
• You use Gmail with many labels
• The server has less than 4 GB of RAM
• The database runs on a slow disk
• Using shared hosting

Nextcloud Mail can’t replace a full desktop email client for very large mailboxes. Still, there is a trick to tackle, which I’ll explain next.

Keep Email Access Fast with a Local Backup

When Nextcloud Mail struggles with very large mailboxes, the main difficulty is data access. In that case, depending only on the web interface is not practical.

This is where keeping a local copy of the mailbox becomes very useful. For the same, opt for the SysTools IMAP Backup Software to download the entire mailbox from the IMAP server directly to your system in formats like PST, MBOX, EML, PDF, or EML.

This backup is independent of Nextcloud. It does not rely on the Mail app or server performance.

Author’s Verdict

Whenever users find Nextcloud Mail slow, the first thing they thought it is an IMAP problem. But, after this discussion, I hope you now understand not only IMAP, but also that other factors lead to this error. If your Nextcloud Mail is slow, don’t remove IMAP account or change the mail provider. Fix the server and caching first.