But do you know how this bug was introduced ? I checked the history of that file and don't see anything introduced recently that might cause this: https://github.com/dovecot/core/commits/master/src/lib-http/http-client-requ... The only one that might be somewhat related is this one from Apr 27 by Stephan Bosch https://github.com/dovecot/core/commit/799b52accf71e86756dde738d22c1c6a500a7... On Saturday, 31/10/2020 at 08:40 John Fawcett wrote: On 31/10/2020 00:18, Scott Q. wrote: I have implemented this change and the core dumps went away. It appears so far that it's indeed the right fix. Has this change been introduced in 2.3.11.3 ? Thanks! I've also been running it for 4 days without any further panics / segfaults and no noticed adverse effects. I'd recommend the dovecot team to consider including the patch in the next update. John diff -ur dovecot-2.3.11.3-orig/src/lib-http/http-client-request.c dovecot-2.3.11.3/src/lib-http/http-client-request.c --- dovecot-2.3.11.3-orig/src/lib-http/http-client-request.c 2020-08-12 14:20:41.000000000 +0200 +++ dovecot-2.3.11.3/src/lib-http/http-client-request.c 2020-10-27 13:06:09.352973130 +0100 @@ -1229,12 +1229,12 @@ const char *error; uoff_t offset; - i_assert(req->payload_input != NULL); - i_assert(req->payload_output != NULL); - if (req->payload_finished) return http_client_request_finish_payload_out(req); + i_assert(req->payload_input != NULL); + i_assert(req->payload_output != NULL); + io_remove(&conn->io_req_payload); /* chunked ostream needs to write to the parent stream's buffer */