What is the size limit for attachments to a ticket reply?

Freshdesk lets you send and receive emails with an attachment size limit of 20 MB/conversation for accounts on the Blossom and above plans. For Sprout and trial accounts, the attachment size limit is 15 MB. 

By default, the content of the email (excluding attachments) has a 15 MB limit per conversation.

However, if you are looking to attach bigger files, you can use Dropbox as a workaround. Once you integrate Freshdesk with Dropbox, you can hotlink any file from your Dropbox account (with unlimited file size), and use it as an attachment inside Freshdesk. This file can be directly opened from Dropbox whenever someone clicks on it, and will not be stored anywhere on our end. Another alternative is OneDrive which could also help you add files with a greater MB value.

Note: We do not recommend that you use heavy HTML content inside your tickets. Instead, you can attach them as separate files inside the ticket just like any other attachment.