Comment 1 for bug 46076

This is most likely not a bug, this is intended by design. pbm2g3-output sendfaxing through an USR V.everything works perfectly for me.

The mgetty-pbm2g3 is different from netpbm-pbmtog3 because there are only some resolutions making sense when preparing data for sendfax. See "man pbm2g3" for more:

-w <page width> sets the width of the resulting G3 page. Default is 1728. If you want to be able to fax it with sendfax, don’t use anything else. For other fax programs, 2048, 2432, 864 and 1216 may be useful. For other purposes, use what you like.

Most likely the init-string for your modem is wrong, resulting in an excedingly high or low resolution. See the sendfax-manual about initializing your modem in /etc/inittab