Answer by Zoredache for Delete files specified by the output of find: rm thinks argument list is too long.

Well I would be tempted to do something like this instead, making the entire operation a single command.

find /home/domain/imap/domain.com/ -mtime +190 \     \( -ipath '*/Maildir/new/*' -o -ipath '*/Maildir/cur/*' \) \     -delete