Empty Subject Line Bug in MailButler for Apple Mail

Last Updated: Aug 04, 2021

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A bug in MailButler, a popular Apple Mail plugin, results in an empty subject line when replying to individual emails. The problem seems to affect only Exchange accounts, and there is currently no fix available. The good news is, there is a workaround.

I am a huge fan of MailButler and have been using the productivity tool and Apple Mail plugin for a couple of months. A few weeks ago, I noticed that Apple Mail started crashing more often than usual. I have been using Beta versions of macOS since Apple released macOS 10.12 Sierra. So the occasional crash of individual applications isn’t unusual.

I also noticed that when replying to individual emails, the subject line of my reply in the composer window would be empty. At first, the issue only occurred every few days and I could quickly, albeit temporarily, fix it by restarting Apple Mail.

Recently, I found myself restarting Apple Mail multiple times a day and so I spent more time narrowing down the cause.

MailButler and Exchange

To narrow down the offending component that was causing the issue, I disabled all Apple Mail plugin using a free tool from SmallCubed called Mail Plugin Manager. Without any plugins enabled, I worked with Apple Mail for a full day without experiencing any issues.

Update: The Mail Plugin Manager does not seem to be available for download anymore.

Next, I enabled Mail Act-On, one of my other productivity tools I use on a daily basis. Another day had passed without the issue occurring, so I reenabled MailButler and the problem returned.

As part of my testing, I realized that the issue would only occur with my work account. It’s an Exchange (Office 365) account, whereas my other email accounts are IMAP and didn’t experience the problem. A few days ago, I migrated two of my personal IMAP accounts to Office 365 and the ’empty subject line’ issues suddenly affected those accounts as well.

Unknown cause

I reached out to Feingeist, the company behind MailButler and after a while, they confirmed that other customers reported the same issue. Interestingly, not all their users with Exchange accounts are affected, which appears to make finding the cause more complicated.

As of this writing, Feingeist doesn’t know what is causing the issue in Apple Mail. But they assured me, that the matter is currently being investigated with high priority.

Workaround for the ’empty subject line’ bug

The good news is that you can temporarily fix the problem by restarting Apple Mail. I hope Feingeist finds the cause and fixes the problem soon. When that happens, I will let you know by updating this article.

Update 2017-10-04: Feingeist released a new beta version of MailButler (Build 6894) that contains “some more changes related to Exchange accounts (missing subject line).”

47 thoughts on “Empty Subject Line Bug in MailButler for Apple Mail”

  1. Another huge fan of Mailbutler. For me, the problem has recently started after I upgraded to OS Sierra. Can’t believe mailbutler has not still resolved the issue. Unfortunately, I won’t be renewing my third year subscription in March.

  2. After 2 days with Mailbutler (version 6901, not the new beta) this bug is now dead… On High Sierra.

    This is verified by Feingeist support, who emailed me to say they’ve fixed it on High Sierra.

    So there you go, you can use Mailbutler without the annoying bug, only if you update your OS.

  3. I too have this issue, like many above, for months now.

    I just upgraded to High Sierra. I’ll keep you posted if that helped solve the issue with MailButler. If it does, I’m thinking of upgrading to the business account. If the issue still exists however, I will uninstall MailButler and will not return…

  4. Thanks for this threat. I just installed Butler and figured it was the cause of my subject line disappearing when replying to an email. One advantage: it’s not a bad idea to update subject lines when sending replies. Still, would be nice to have the original subject the default. Any updates on fixes?

    • Unfortunately, I cannot confirm that the beta release addresses the problem. After installing it, and restarting Mail twice (at Butler’s request), I am now still seeing exactly the same problem (in Exchange, of course): no data in cc field; empty subject line when replying

      • Same here – the problem still exists. I am about to deinstall and cancel my subscription. @Feingeist Team: Help, please! You are loosing customers!

    • The support team emailed me back to say that they are releasing a new version before end of September which they are hoping resolves this. Fingers crossed. Love Mailbutler but this subject line issue is a real problem.

      “We are also currently working on a new version of MailButler with a different technical mechanism how to handle Exchange accounts. The release date should be next week before the end of September, We kindly ask you for some more patience.”

  5. Really appreciate your thorough description of the problem! This has been driving me crazy for a while now & I’m restarting mail about 30 times each day! I hope they find a fix soon because I think Mailbutler is awesome and don’t want to get rid of it because of this.

  6. +1 here too – exactly as Michael described it.

    I definitely appreciate the value that mail butler can bring to our email workflows, but this bug is a deal-killer for me, and it sounds like several people here would agree.

    I hope the MailButler team can figure this out soon!

  7. I have the same problem, it is terribly frustrating and restarting Mail only works for an email or two. Mail Butler, PLEASE FIX IT!

    • Another with the same problem. I was able to logoff MB and then logon again and the problem went away (temporarily of course) but at least i don’t have to shut down Mail.

  8. Thanks for your efforts and explanation. I hope it will be resolved soon… can imagine it has high priority as this does not increase productivity at all :(

  9. Same problem. I’ve been on with Apple many times and also mail Butler support (which by the way is not very good). They thought initially their new update caused the problem and walked me through re-installing the old version. This did not help so I’m still experiencing the problem. The weird thing is it is intermittent with forwards and replies. Sometimes it works find, sometimes not. I sure wish they would fix it soon; it’s a pain right now.

  10. I have the same issue. It’s becoming very annoying hacving to restart mail.app multiple times a day. I love Mailbutler but I have had thoughts of dumping it until the issue is resolved.

        • Another problem I discovered is that Apple Mail with Mailbuter sometimes hides the recipient list (To: list), and it’s hard to tell who else is on the email. Sometimes replied all doesn’t capture all the people listed if they are not shown. I uninstalled the program even though I like it a lot. These bugs need to be squashed before I reinstall.

  11. Hi, and thanks, Michael, for spreading the light on this issue! Our developer team has indeed been occupied with the solution for some time now, and we are coming closer; yet, the problem still exists for some of our users.

    Good news is: we’re preparing a brand new update that will for sure solve the problem once and for all. This hasn’t been officially announced yet.

    Of course, we’ll continue to provide compatibility and development of Mailbutler for Apple Mail, too.

    • I appreciate that you are excited about Mailbutler going Gmail, but fail to see how this will accept our collective Exchange-Account-Problems. In our corporate environments, IT is surely not going to let us migrate from the company’s exchange server to Gmail to fix a problem with a plugin. It is absolutely essential to fix this, and fix it swiftly and consistently. It makes Mailbutler simply unusable for anyone using an Exchange-Account. This bug has been around for more than 2 months.

  12. Thanks, same issue here. I’m a new Mailbutler user for 2 days and this is also happening on my Exchange account. I also use Office 365. Appreciate the “restart” tip, I’ve just been copying the subject line from the email below which also works. Will appreciate the fix, hopefully Mr. Feingeist can find it as I like his plug in so far.

  13. +1. I’ve uninstalled on both my work and home machines until this issue is addressed. In addition to the empty subject line error, messages are often missing the To and CC information. A restart of Mail fixes both issues temporarily, but it’s maddening.

  14. I was having the same problem. MacOS Sierra, latest update to MailButler, using Exchange email. Subject line was being deleted and it was also removing anyone CC’d on a message.

    Here is a fix that is working for me for now – Restarting Mail alone did not work for me at all. But here is what did work:

    I quick Mail, then opened up Activity Monitor. I was able to quit MailButler that was still running with Mail inactive. Then I reopened Mail. MailButler restarted after opening Mail, and the error is gone.

  15. having the exact same problem. restarting every time is not a good solution for me. going to uninstall the Butler…

  16. same issue here. It has been an intermittent issue, but since the last update on it is happening was too often. I only updated my MBA and noticed the issue increasing. I did not upgrade to latest version of MailButler on my iMac and no issue…

  17. I thought I was the only one having this issue. Feingeist even pushed me to a new beta in hopes to fix the bug, but it didn’t resolve the issue.


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