I have configured my autosupport SMTP Mail Host to use "smtphost" which is what the email team told me to use.
When I type nslookup smtphost I get a list of eight IP addresses returned, each belongs to a different server and the servers are split across 2 sites. I imagine this is a common setup in a large company. One or two of these servers seem to be less reliable than the others. I sometimes get that wacky FTP: weird server reply but the autosupport will go eventually. I suppose on the retry it will get a good SMTP server.
I don't want to use a list of IP addresses for the SMTP Mail Host because they might change.
After some discussion with colleagues, listing the mailhost name multiple times in the AutoSupport configuration might speed things up, if:
DNS resolution round-robins multiple SMTP server IP addresses
The connection errors out immediately (e.g. 421 Service Not Available)
This is because an immediate connection failure results in the AutoSupport daemon moving on to the next configured SMTP server entry, immediately. Otherwise, the AutoSupport retry logic kicks in, where (by default) retries are attempted every 4 minutes, 15 times.