Your postfix server block big messages and you want to exchange more than 10MB
This is by design.
To reconfigure your Postfix mail server you have to change the configuration in main.cf. Before doing this you should have a look at the configured default. This can be done with:
To search for something you can pipe this in grep. e.g.
postconf -d | grep -i size
Now you will get all the default information with size in it. The default message size limit is about 10MB.
To change the limit for your mails you need to add or change the following entry:
message_size_limit = 20480000
which is about 20MB. Please note that this configuration is for your mail server only. When you excahnge mails per SMTP, all servers in between need to accept this size. If not, you cannot send mails with this size. In your own maildomain this will not be a problem.
Do not forget to reload the postfix configuration (and do not forget an eventually seconds MX mail server if you have one) and than check it with:
postconf | grep -i size
About the Author
Wim Peeters is electronics engineer with an additional master in IT and over 30 years of experience including time spent in support, development, consulting, training and database administration. Wim has worked with SQL Server since version 6.5. He has developed in C/C++, Java and C# on Windows and Linux in different European countries and different European languages. He writes knowledge base articles to solve IT problems and publishes them on the Lubby Knowledge Platform where he is one of the most important contributors and the main developer.