Post workers will now have to sort through a backlog of millions of letters and packages that piled up over a month in which 30,000 of their number went on strike.
The backlog is much worse in some regions than others, said Post spokeswoman Melanie Kreis on Sunday.
The eastern states are particularly badly affected, while residents of Berlin and Munich are also likely to have to wait patiently for a few days before letters finally reach their destination.
"We are working on reducing the backlog as quickly as we can," said Kreis.
Kreis praised the agreement as being "the complete package, which offers our workers security and a future as well as allowing for growth in the company."
A central bone of contention in the negotiations was smaller regional package delivery services being set up by the Post which offer worse salaries and undercut the job security of post workers.
While the Post was able to hold onto this new business project in the agreement, it ruled out widening it to include letter delivery services.
Kreis now projects that almost 15,000 new jobs will be created in the package delivery service up until 2020.
"We are very happy with the agreement," said Andrea Kocsis, the union's chief negotiator.
"It fulfills the desire of Post employees for the correct amount of security. Without their strikes that wouldn't have been possible."