row length in mail messages

If I send a e-mail with mail() (or a mail client) as plain text all rows are limited to ~70 chars and imag data is 72 chars long and continues in the next row.

This is bad for longer URL's. Does someone know a page with specifications about these length

I don't, but I will advice you to take a look at the phpmailer class. It is a complete class so they will have solved this.

http://phpmailer.sourceforge.net/

hehe, the funny thing is that the length is set automaticly by the mail function, try it: send a mail with 100 text length inside the mail function.