Why am I getting an email size error with SQL Server database mail? I am sending 6 .csv files as attachments through SQL Server Email. But Email is failing with the following message in the database mail log:

Exception Message: Cannot send mails to mail server. (Service not
available, closing transmission channel. The server response was: DATA
length exceeds 52.4MiB limit)

Then I ran the following command to increase the maxfilesize limit 2 GB
EXECUTE msdb.dbo.sysmail_configure_sp  
'MaxFileSize', '2147483647';

Filesize limit was changed successfully to 2 GB, but still I am getting the same error message.
Following are my file sizes in KBs
File A    213   KB,
File B    265   KB,
File C    6246  KB,
File D    35    KB,
File E    60    KB,
File F    31371 KB
I am using mail-gun(smtp) to send an email. Email is running successfully without FILE F. But When I attached FILE F, email fails. Why my email is failing when I increased maxfile size to 2 GB. Any Idea?
You mentioned that you're using Mailgun as your mail server. Mailgun's terms page say they limit email sizes:

An individual email message may not exceed the per-message size limit
(including attachments) of 25MB or it may be permanently lost.

You'll want to reduce your email sizes to match, or consider using a different SMTP server.