Address:

Sala (= office) 4014,
Departamento de Matemática,
Instituto de Ciências Exatas,
Universidade Federal de Minas Gerais,
Av. Antônio Carlos 6627,
Brasil
CEP (= post-code): 31270-901

Phone:

(+55) 31-3409-1422

Emails:

john.macquarrie[at]gmail[dot]com
john[at]mat[dot]ufmg[dot]br

Current odds of success:

Private email: 90%,
Institutional email: 80%,
Sending a letter: 98% (I guess, though I've never tried),
Knocking on my door: 50%
Phoning: 48% (slightly less than knocking due to small chance phone is broke or I just don't want to answer)