Attachment file size limit when sending mails

Erpnext not sending email if attachment file size is greater than 5 mb.Mail status(error or send) not shows if the file size is greater than 5 mb

Yes there is an attachment limit of 5 MB. I would suggest send your attachments in parts.

We mainly send pdf file from pdf file may be with size greater than 10 mb.can i increase the size limit ?

Unfortunately that will not be possible.