It took quite a lot of time to find out that the version 1.4.3 doesn't support a quite typical format for the DLR timestamps, so I'll document it here for the other people that might be affected. kannel 1.4.3 supports without issues the format defined in the SMPP specification 3.4 for DLR timestamps (YYMMDDhhmm) (Appendix B), but it's common now to find providers using a format with seconds (YYMMDDhhmmss). Kannel 1.4.3 won't be able to read that timestamp and will mark all the replies as if there was a malformed response.
There is a patch in kannel source tree to change this, but probably involves more changes to work (simply applying the patch doesn't work) https://redmine.kannel.org/projects/kannel/repository/revisions/4749/diff/trunk/gw/smsc/smsc_smpp.c So the people using debian should be aware of this, a working .deb with 1.5 can be found here -> https://redmine.kannel.org/projects/kannel/files By the way, since 1.5.0 has been pretty stable for at least one year (according to the mailing list), are there any plans to retag the 1.5 as the current stable?
