Does any email software receive signed emails?

Yes, any email software is able to receive signed emails.

Sotware that cannot handle S/MIME (they can't interpret the signature), provides an attached file named smime.p7s that carries the signature. The remaining part of the email is normal.

S/MIME-compatible software displays a distinctive sign: label, lock, paper and pen, etc. to symbolize the signature. More than 97% of email software handle the S/MIME standard.

Webmail services (such as gmail, yahoo, mail, etc.) handle the S/MIME standard when receipting. On the contrary they cannot send signed emails.

As always with IT matters, it still exists a few software that are not S/MIME-compatible, or worse, that display an error. It is often former version that have been corrected and just need to be updated.

There also are some email servers that simply destroy signed messages. See A correspondent indicates "The digital signature is not valid"