Mail.log file shows too much IMAP activity from Android phones

I’ve been running a MIAB server since September, and it’s working pretty well. Starting around January 8th, the load on the server is up, and the mail.log file shows constant activity from two of my friends who have Android phones. My mail.log file ending January 6th is 8.0M large, and the log file ending January 14th is 966M large. In the past 36 hours, the current mail.log file is already 545M large.

Has anyone else noticed Android phones generating multiple lines per second each second in the mail.log file? Fortunately, I’m on an NVMe disk, so I’m not suffering any noticeable performance issues, however, I would like to address the root cause, since I’m sure others are experiencing the same issue.

I’m not really sure what changed, but shortly after midnight today, the activity returned back to normal. My VPS has 1 CPU, and the load has been hovering around 4 for the past week. Now it is back to the usual 0.20.

Seems to me that the default mail client on Android phones logs into the server (my server at least) every 9 seconds. We have not figured exactly the issue, but so far getting the user to actually get Gmail’s app instead seems to work.
We have also noticed that setting up Outlook on Androids with the shortcuts it offers lists the MiaB server as an exchange server and then it checks-in every 9 seconds as well. We are not completely certain about this via Outlook; we are trying as more of my client’s users get on my new email server (MiaB).

So don’t take this as a definitive answer…it is more of a “oh yeah it seems like that happens to me too” answer.

Yes, I’ve noticed that the default mail client of Android phones tends to log in every 9 seconds. After my first Android friend set up his phone to check mail, I noticed that my old server began having some performance issues. Once my second Android friend set up his account, the performance even got worse, so I had to upgrade from a VPS that used HDD to one that used NVMe. I did the upgrade on December 12th.

That solved the performance issues, but then their phones went from checking IMAP once every 9 seconds to checking multiple times per second. This happened between January 8th and the 15th. It looks like the problem went away on its own for the most part, but occasionally the load is still spiking to 2.0.

If this continues to be an issue, I’ll ask that they explore the Gmail app. I know that this is not really a MIAB issue, but I’m surprised that nobody else is complaining that Android phones are essentially performing DoS attacks on IMAP servers.

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I have only ever used K9 mail client on Android and it has always worked without issue. If K9 is an option for you, give it a try and see if the problem disappears.

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