attachment tooo big and error coming in all time

I use my gmail account to this service.  And by mistake I sent attachment to big I think I delete the outgoing however this message comes everytime I use this service: 
“IMAP Unable to upload message “XXXXX” Different Options to folger Gmail/trash”. ALERT Message too large. 
Please let me know how to delete complete from this email client… Thanks in advance… 

FIX IT !!!  Thanks anyway… Was on TRASH folder … I delete from there and thats it…