For some reason my older emails get deleted from the BB.

I use TMO. I have setup 2 yahoo accounts and one work account (web based).

Lately, in all the 3 accounts most of the emails get deleted automatically. I can't see emails past yesterday. This happens randaomly after couple of days.

I have enough free space. Free space in card is 375 MB.

OS is v4.2.0.64.

E-mail messages do not get stored on the media card... so that part is largely irrelevant.
How much free memory is in your actual device?
Also, if you go into 'Options' within your messages module on the Blackberry... how long is the 'Keep Messages:' setting? (Within General Options.)

Don't look at the SD card for free space look at the BB device memory...
Options, Status. What does that say?

Is it loosing the call logs also? Look at Messages > View Folder > Phone Call Logs.
Read this and proceed:
Why is my 8100 Pearl losing its call logs or message logs? - BlackBerryFAQ

microSD card space doesn't equal having enough space on the handheld. How much space do you have free on your handheld?

Options -> Status -> "File Free:"

status:
file free: 578,572 bytes
file total: 65,142,784 bytes


messages->general options
keep messages: 30 days --- so it should not delete emails few days old

Nope. Are you on BES? Did you delete any emails there? or on your Yahoo account?

I deleted the other language support and the device mem went up to 12MB free!

Will see if this solves the problem.

some of my emails are being deleted after i read them once. why is that?