1. Empty Trash & Spam Regularly
   These folders often hold hundreds of MBs of junk. Clear them out to reclaim space.
2. Use Search Filter size:10M
   Identify and delete large emails using this filter in the search bar.
3. Remove Old Attachments
   Download important attachments and delete emails that are no longer needed.
4. Delete Unused Promotional Emails
   Search by sender or keywords to bulk delete marketing and newsletter emails.
5. Clean Sent Folder
   Often overlooked, this folder can accumulate large files over time.
6. Use Search Filter older_than:2y
   Bulk delete emails older than 2 years to free up storage fast.
7. Forward Emails to Another Account
   Send important emails to Gmail or Outlook, then delete from Yahoo.
8. Download Emails as PDF or EML
   Manually save essential emails to your computer for offline storage.
9. Upgrade Yahoo Mail Plan
   Consider Yahoo Mail Plus or 100GB/1.2TB plans if you want more online space.
10. Use an Email Backup Solution
    Quickly archive and offload your Yahoo emails to local storage or another email service without data loss.
    Read more for a detailed guide. - Yahoo Mail Storage Limit
    

I’ve been using ProtonMail for a while now, but I recently decided to switch to Yahoo Mail to better sync with my other email accounts. The issue I ran into was finding a way to move all my emails—especially with attachments and folders—over to Yahoo without losing anything.

After a bit of research, I found a tool called eSoftTools ProtonMail Backup & Migration Software. It turned out to be really useful. The software lets you log into your ProtonMail account securely, and then select Yahoo Mail as the destination. What I liked most was the option to choose specific folders or use a date filter to only migrate the emails I actually needed. It also kept the email formatting and attachments intact during the process.

Read More - Migrate ProtonMail Emails to Yahoo Mail