Email status showing "Queued" for all emails

[krishna7whds]

I running Multi site with E-commerce, since last three days all emails stuck in "Queued" status. we haven't updated anything on server and code level, but suddenly it started to queue all emails.
I using server level cron and scheduled it for every minute .
I have reinstalled, deactivated and re-activated plugin, no luck.

can any one please help me, its been more than 400 emails stuck in queued status