I confirm the workaround presented by Seb: I disabled photographs in the message preview and had no more 'Formatting message' deadlocks (Edit -> Preferences -> Mail Preferences -> Headers -> Show the photograph of sender in the message preview).
There is a related bug filed in Bugzilla: Bug #578577 - deadlock in contact image lookup leading to evo hang formatting message (https://bugzilla.gnome.org/show_bug.cgi?id=578577).
I confirm the workaround presented by Seb: I disabled photographs in the message preview and had no more 'Formatting message' deadlocks (Edit -> Preferences -> Mail Preferences -> Headers -> Show the photograph of sender in the message preview).
There is a related bug filed in Bugzilla: Bug #578577 - deadlock in contact image lookup leading to evo hang formatting message (https:/ /bugzilla. gnome.org/ show_bug. cgi?id= 578577).