How to install DH params 2048 on Dovecot Debian?

Question

Debian

Good day, Dear Readers!
I address you on the following issue: The server is running Debian 7 wheezy, software (exim4-4.80-7+deb7u3)+(dovecot-pop3d-2.1.7-7+deb7u1).
It is necessary to set DH params for Dovecot equal to 2048 or 4096. The default is 1024. The
difficulty is this: when you add a parameter to the config

ssl_dh_parameters_length = 2048

then dovecot says it doesn't know such a parameter.
Can you please tell me where and how to set this parameter correctly? I've already read enough information, but I don't understand something.
On the second server, Debian 8 and Dovecot 2.2.13-12~deb8u1 are installed, this parameter is successful, but on the old version, it still doesn't work.
Thanks in advance for your replies!

Answer 1

In general, after reading a bunch of official documentation, I realized that this version only supports 1024.
I solved the problem this way: I added an entry to /etc/apt/sources.list
And from the new repository I updated dovecot to the latest version, after which everything started up successfully!