We switch email clients from time to time, and when we do, we need to migrate the local email history from one application to the other. This may seem easy, because email clients generally include migration assistants and store emails in standard formats, for example,
.mbox. But recently I was migrating from Thunderbird to Apple Mail and these tools failed: they either lost emails, or concatenated all emails together, or created a new mailbox for each email.
Email migration should be easy, yet I suffered from all these ridiculous problems, so I developed the ultimate solution: setting up a local email server. An email server is the common denominator between otherwise incompatible email clients, but common email servers (for example, iCloud and Gmail) are impractical for email migration. While simpler to use, these email servers would require uploading the whole local email history only to re-download it in a new email client. With a local email server we accelerate an email migration that could take days to a few hours.