A probably dumb question, but I'm stumped

[Christy S]

Hi folks,

I'm stumped on an error we're getting in dovecot after upgrading ubuntu. 
I will say up front that I'm far from a linux expert. I'm helping my 
husband by managing a virtual private server to handle his domain, 
including its email. We set this up two years ago and once I finally got 
the mail working, it's been humming along just fine since, until two 
days ago when I performed the ubuntu upgrade. Now, when we try to send 
mail through his domain thunderbird gives this error:

Your message was sent but a copy was not placed in your sent folder 
(Sent) due to network or file access errors.

Note that it says this, but the mail isn't actually sent at all. We are 
using SSL and have been since the beginning which might be part of our 
problem, but I'm not positive.

A google search suggested adding two lines to the 10-ssl.conf file.

ssl_dh = </usr/share/dovecot/dh.pem
ssl_cipher_list = HIGH:!DH:!aNULL

I did both of these things and restarted the server completely, but no 
luck. looking in /var/log/mail.err I see this.

Nov 29 14:08:56 kylesmith-music dovecot: imap-login: Error: Failed to 
initialize SSL server context: Can't load SSL cert
ificate: error:140AB18F:SSL routines:SSL_CTX_use_certificate:ee key too 
small: user=<>, rip=xxx.xxx.xxx.xxx, lip=xxx.xxx.xxx.xxx, 
session=<t4qrdkS1kPNLFhL4>
What's interesting is that last line only showed up after I added the 
two lines to the config file.

My guess is I need to do something with SSL, update it maybe? But I 
don't want to go fiddling around purely on a guess and potentially break 
things even more. So, any of you much more linux familiar types want to 
point me in the right direction? Thanks!

Christy