At https://github.com/manzinello/mailgo the author wrote:
Unfortunately mailgo is not actively maintained anymore. I'm sorry for this but I personally don't have time to maintain it... I hope someone will take over the project.
a) Write a notice in the module description, then wait until someone else is taking over maintenance of mailgo
b) Drop this module to "not maintained" as well
c) Maintain mailgo yourself
Decide.
Needs review
1.0
Miscellaneous
@guedressel thanks for opening this issue, I haven't had enough time to support the module lately. I added D10 support now. I'll test if everything works good there and will make a new beta/rc release.