On Fri, Feb 14, 2025 at 11:30:53AM +0200, Nikolaos Milas via Postfix-users
wrote:
> Jan 14 10:37:12 mailgw1 postfix/smtpd[1125361]: warning: hostname
> smtpfra7.fortimailcloud.com does not resolve to address 154.52.2.249: Name
> or service not known
This host seems to have ~46 A records:
$ dig +short -t a smtpfra7.fortimailcloud.com | sort | fmt
154.52.2.141 154.52.2.142 154.52.2.143 154.52.2.144 154.52.2.145
154.52.2.146 154.52.2.147 154.52.2.148 154.52.2.149 154.52.2.150
154.52.2.151 154.52.2.152 154.52.2.153 154.52.2.154 154.52.2.155
154.52.2.156 154.52.2.157 154.52.2.158 154.52.2.224 154.52.2.225
154.52.2.226 154.52.2.227 154.52.2.228 154.52.2.229 154.52.2.230
154.52.2.231 154.52.2.232 154.52.2.233 154.52.2.234 154.52.2.235
154.52.2.236 154.52.2.237 154.52.2.238 154.52.2.239 154.52.2.240
154.52.2.241 154.52.2.242 154.52.2.243 154.52.2.244 154.52.2.245
154.52.2.246 154.52.2.247 154.52.2.248 154.52.2.249 154.52.2.250
154.52.2.251
Some versions of glibc have had trouble with this many addresses, and
perhaps your Postfix can't reliably resolve this name to a list of
addresses that includes that address. Perhaps the lookups are taking
long enough for the client to disconnect in the meantime.
The Postfix source distribution contains an auxiliary/name-addr-test
directory, where you'll find "getaddrinfo.c". Compile it:
$ cc -o getaddrinfo getaddrinfo.c
and run it a few times to see how long lookups take and whether they
work reliably:
$ ./getaddrinfo smtpfra7.fortimailcloud.com
Hostname: smtpfra7.fortimailcloud.com
Addresses: 154.52.2.232 154.52.2.147 154.52.2.149 154.52.2.229
154.52.2.152 154.52.2.224 154.52.2.142 154.52.2.227 154.52.2.155 154.52.2.241
154.52.2.148 154.52.2.156 154.52.2.151 154.52.2.245 154.52.2.158 154.52.2.247
154.52.2.230 154.52.2.153 154.52.2.141 154.52.2.233 154.52.2.228 154.52.2.234
154.52.2.236 154.52.2.239 154.52.2.244 154.52.2.150 154.52.2.144 154.52.2.242
154.52.2.248 154.52.2.231 154.52.2.243 154.52.2.246 154.52.2.146 154.52.2.154
154.52.2.249 154.52.2.225 154.52.2.157 154.52.2.250 154.52.2.240 154.52.2.237
154.52.2.226 154.52.2.235 154.52.2.143 154.52.2.145 154.52.2.238 154.52.2.251
Run the separate tests spaced out in time to try to avoid getting cached
results.
--
Viktor.
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