Hi Katrin, I have taken (1) mysql dump and (2) customized opac templates backup from Koha 16.11 where postfix MTA was used for email alerts and restored the said files to Koha 18.05 on Ubuntu 16.04 Desktop and Posftix is not installed. Apart from this, I have not made any changes. Is there any other files to be taken backup for migrations? with thanks. Satish