Zimbra: Configuring maxmessagesize

# Switch to Zimbra user
su -u zimbra
 
# Check Postfix
postconf message_size_limit
message_size_limit = 10240000
 
# Set postfix
zmprov modifyConfig zimbraMtaMaxMessageSize 50000000
postfix reload
 
#Set IMAP globally
zmprov modifyConfig zimbraFileUploadMaxSize 50000000
 
# Set IMAP per domain
zmprov modifyServer mail2.domain.com zimbraFileUploadMaxSize 50000000

Restart Zimbra after executing this