Man pages matching name net::smtp::tls::butmaintained in section 3pm:

Net::SMTP::TLS::ButMaintained.3pm.en	debian 10 / libnet-smtp-tls-butmaintained-perl
Net::SMTP::TLS::ButMaintained.3pm.en	debian 11 / libnet-smtp-tls-butmaintained-perl
Net::SMTP::TLS::ButMaintained.3pm.en	debian 12 / libnet-smtp-tls-butmaintained-perl