I have a 6s. Older emails disappear after a few days.

[iMore Question]

Is there a way to retrieve them?

 

[Just_Me_D]

Are they disappearing from view on your device? If they are still visible when you log into your email account via a web browser then it's a settings issue. Go to the Mail settings, choose the email account and then look for a setting similar to "Mail Days to Sync", and then alter the setting accordingly.