Tucows is primarily a domain registration and hosting company. They do provide mail service for their customers.
Delivering to tucows
There is very little information available about delivering to domains hosted by Tucows.
Important links and references
Tucows does not provide postmaster pages.
Tucows does provide a FBL administered by Return Path. Applications are accepted at the Tucows FBL signup page.
Tucows does not offer a whitelist for senders.
Tucows uses the Return Path Certified whitelist in mail delivery decisions. Mail from IPs on the Return Path Certified list will see better delivery at Tucows domains.
Support for Senders
Tucows does not provide any support for senders.
Tucows has not published any information about commercial spamfilters they may use.