RFC6761 states about example domains (such as example.com):
Application software SHOULD NOT recognize example names as special and SHOULD use example names as they would other domain names.
Currently, these example domains are set up with a webserver that explains their purpose. The domains lack any MX records; it doesn't have a null MX record either. Because of this, an MTA will try to deliver mail to the A record, which is the IP of the web server, which doesn't accept mail, causing mail to be queued on my MTA until it eventually expires.
Clearly, following RFC6761 doesn't work so well if you're a postmaster.
Are there disadvantages to rejecting all mail to example addresses? Are there any sources that have a recommendation about this?
EDIT For context: We automatically check queue size and if it gets too big someone has to manually check why that is happening. Lately this happens because of one application sending to example domains. Naturally, it should not do that and the correct solution is to fix the application, but that's not going to happen for reasons I won't get into. Since that is the situation, I feel rejecting mails in our mail filters is a better solution than ignoring mails in our alerting software.
FWIW: I agree with the "you should not need to do this" sentiment, but sometimes the world is not perfect.