The duration necessary for bulk migratory conversion of MSG files into Mozilla Thunderbird varies based on how many individual MSG files you're converting, as well as their sizes. For small conversions (dozens of emails), expect approximately 5-15 minute conversions (total time). For larger volumes (hundreds to thousands of MSG files), total conversion time is likely to take anywhere from 10 to 30 minutes, depending on your system's speed and the method you choose to use. When using a secure and dependable conversion tool, such as GainTools MSG to MBOX Converter, this conversion process will not only go quicker, but it will also happen without any data loss. GainTools also provides a free trial test phase which allows you to check out the conversion results prior to performing huge bulk conversion tasks.