I need an email server, or something

[Michael Hipp]

I support Linux servers scattered hither and yon. I'd like for them to 
send me various emails when bad things happen or to report on this or that.

Problem is, many of them are served by ISPs whose smtp server requires 
authentication. I often do not have access to the login credentials. I 
don't want to store login credentials for my own email server on these 
servers owned by clients (and not under my physical control). 
Additionally, lots of these ISPs block outbound port 25.

Any ideas on how I can get my servers to send me things?

Is there an email server somewhere I can use?

Surely I'm not the first to bump up against this.

Perplexed in Arkansas,
Michael