$ du -sh ~/.local/share/evolution/mail/ 6,1G /home/banana/.local/share/evolution/mail/It is nothing when compared to the size of a modern disk. And those disks have become quite cheap: nowadays, US$ 200 are enough to buy a USB 3 external hard drive with 3TB of space (~500 times the space the 62,000 e-mails occupy).
Where do you backup? Backups are a must!