Thunderbird Inbox Full Cannot Receive Email Error – Resolve

admin | November 20th, 2017 | Mozilla Thunderbird

Mozilla Thunderbird, a renowned email client application that does not need any introduction. Every user is aware of its functionality and its advanced features. But like any other software, it also has led to some difficulties and errors that require immediate attention. Among the long list of errors, the mostly faces issue by the user’s is “Thunderbird inbox full cannot receive email”. The problem results in – Thunderbird mailbox full error message which affects the entire exchange of messages activity.

This blog will help you understand the situations that lead you to this message alongside its various solutions. But first, let’s take a look at the user scenario to perceive knowledge about the exact situation.

Last week I encountered an Alert! The folder Inbox is full and cannot hold any more messages. And to my understanding, I made some space for more messages by erasing some old and unnecessary mails and compact the folder. This activity reduces the size of my inbox to approximately half. Moreover, surprisingly I faced the same alert message once again the next day. “Thunderbird inbox full cannot receive email” error also forced to have my attention. I am facing such errors for the very first time and my Internet Service provider also proved to be unhelpful.  I have tried all possible solutions that I can think of to resolve Thunderbird says inbox is full alert. Even Mozilla Thunderbird re-installation dis not work. Now, I am even ready to speak with an expert to know a resolution method as soon as possible. Can please someone help me out?”


The user can take an idea of what could be happened if the situation is not taken under control. The problem will create more intense issues which will affect the daily business activities. So, an expert suggested solution, as well as some manual approaches are discussed in the following sections.

Expert Advice to Solve Thunderbird mailbox full error message

Let’s start by giving you an expert advice. The Thunderbird says inbox is full error can easily be resolved with the help of a standalone tool that will save you the trouble of deleting or shifting the emails. A tool like Convert MBOX to PST will migrate all your Thunderbird emails to PST file format allowing you end emails gain. Use of the software is the best choice when you want fast and better results which is not possible in case of manual solutions. Even a less technical person can use the utility as it has a user-friendly interface. Additional features are also provided to perform an advanced conversion. Otherwise, manual methods are also discussed in the following section as an alternative approach.

Solutions for Thunderbird inbox full cannot receive mail – Error

There are two basic methods used to troubleshoot the error. Compacting and deleting are the commonly used techniques that every user indent to perform. Let’s take a look at them one after the another.

1) Compacting to resolve Thunderbird inbox folder is full issue

Whenever a user deletes a message from Mozilla Thunderbird inbox, the message is only marked as erased or being removed from the mail file. The mail is not actually deleted. Therefore, to properly delete it, you need to compact the folder. Compacting of the folder is considered to be most important part and if it is not performed it will create problems for the user. The size of Thunderbird will grow bigger and bigger until and unless Thunderbird scratched its head. Hence, a user should perform compacting of the folders on regular basis where it can be a weekly task as well. But if done on daily basis then it will be a more quicker task to perform. And if not at all performed then a user will definitely face Thunderbird inbox full cannot receive email error.

2) Deleting to overcome Thunderbird mailbox is full Error

As discussed in User scenario, re-installing of Thunderbird application will hardly solve the error, as the trouble is with the email files which are unaffected by this approach. Hence, other than just compacting, there has to some other way to troubleshoot the Thunderbird inbox full cannot receive email error. The option of deleting the unwanted and incorrect files can be an option.

Note: Mozilla Thunderbird is not able to open the files which are form new emails. Therefore you can migrate email to another folder available in the local hierarchy.

All targetted emails can be transferred in bulk that too at the same time. You can perform this by selecting all emails using a shift key and then drag them to the new folder. But these are very fewer chances that this bulk file migration will cause a full condition. As the folders almost every time consists of few deleted emails stored in them. Hence, while the folder takes some time to copy, the process will be approximately successful.

Also, you must know that the recycle bin is not used by Windows when you delete a mail from Thunderbird. The reason behind this is that the file is too large even for recycle bin to hold on to. Hence, in explorer, you can rename the file instead of deleting it. This will also lead to the smooth working of Thunderbird application. Yet the problem with large files is still not resolved and Thunderbird inbox full cannot receive email error still persists.

Note: User can see that each file is attached to a similar name file with an extension MSF. There are the indexing files which are associated with the folder. So, once you have renamed or deleted the file, you must also delete the associated MSF file with it. Otherwise, Thunderbird will generate a new index to prevent the indexing issues.


Thunderbird inbox full cannot receive email issue occurred by a limitation on the Windows platform with files, having greater than 4 GB size. The inbox or any of the folders in Thunderbird can exceed this size if not compacted or have many emails. Therefore, considering all these things we have discussed the problem of Thunderbird mailbox is full along with the solution that will reduce the size of inbox approximately to half.