I guess it should be changed to:

```ruby
yamlconf = YAML::load(f)
```

Actually this exception is being raised:

```
msf auxiliary(emailer) > run

[-] Auxiliary failed: NameError undefined local variable or method `fileconf' for #<Msf::Modules::Mod617578696c696172792f636c69656e742f736d74702f656d61696c6572::Metasploit3:0x007f9c154f39f0>
[-] Call stack:
[-]   /Users/juan/Projects/git/metasploit-framework/modules/auxiliary/client/smtp/emailer.rb:53:in `block in load_yaml_conf'
[-]   /Users/juan/Projects/git/metasploit-framework/modules/auxiliary/client/smtp/emailer.rb:52:in `open'
[-]   /Users/juan/Projects/git/metasploit-framework/modules/auxiliary/client/smtp/emailer.rb:52:in `load_yaml_conf'
[-]   /Users/juan/Projects/git/metasploit-framework/modules/auxiliary/client/smtp/emailer.rb:94:in `run'
[*] Auxiliary module execution completed

```