I don't use fastmail. I use Office365. It seems that fastmail only does *.domain.com and not *.*.domain.com: https://www.fastmail.help/hc/en-us/articles/360060

I don't use fastmail. I use Office365. It seems that fastmail only does *.domain.com and not *.*.domain.com: https://www.fastmail.help/hc/en-us/articles/360060591053-Plus-addressing-and-subdomain-addressing#subdomain https://www.fastmail.help/hc/en-us/articles/360060591053-Plu... Hope that helps