I was convicted of Mail fraud 16 years ago. Never served time. Paid back taxes and served probation. I have a felony conviction. Can I travel to the United Kingdom. Canada and Ireland?

Depending on the circumstances of the conviction and how it would be considered under Canadian Law than two possiblites exist.

If the conviction holds a sentence of 10 years or more under Canadian Law than you'd need to apply for rehabilitation in order to visit Canada. If the convictionwould carry a 5 year sentence than you would be deemed rehabilitated and may enter Canada (actually you may apply to enter Canada without the need for rehabilitation, it is no guarantee you will be admitted).

Again, it depends on what the exact charge was and the circumstances involved. In some instances you may argue why the conviction would not garner the maximum sentence in Canada.