On 13 May 2019, at 22.56, Root Kev via dovecot <dovecot@dovecot.org> wrote:

May 13 11:35:43 config: Fatal: master: service(config): child 26900 returned error 83 (Out of memory (service config { vsz_limit=1024 MB }, you may need to increase it) - set CORE_OUTOFMEM=1 environment to get core dump)

If you set ssl_dh setting this most likely gets fixed.