[[!meta title="Ruby on Rails: Fix the hostname does not match the server certificate error"]]

## The problem

If you encounter this problem when running Ruby on Rails:

    OpenSSL::SSL::SSLError (hostname "localhost" does not match the server certificate)

it is likely due to 
[ActionMailer](http://api.rubyonrails.org/classes/ActionMailer/Base.html) 
using the **smtp** as the ***delivery_method*** and
your local mail server supporting TLS/SSL, 
but not having a correct/valid certificate.

## The solution

You can add a valid certificate, but if the server is just used 
for sending out mails, this may not be suited.
In that case, you can change the ***delivery_method*** to
**sendmail**, which makes ActionMailer use the sendmail
binary directly.

[[!tag net unix foss ungleich rails]]