Email new issue: Generated address uses characters that Debian/Ubuntu prohibit by default

Summary

I was excited to discover the new "email new issue to project" feature in 8.13/8.14. Unfortunately, when trying it out, I discovered that exim4 (my MTA) rightly refuses to accept the email in the default config shipped by Debian, stating the following:

2016-11-26 20:34:59 (snip) A=cram_md5_server:andreas rejected RCPT <redacted>: restricted characters in address

The issue is the slash present in the email address, which the default config does not allow.

Steps to reproduce

Send a "new issue" email via (at least) the exim4 MTA as configured by default in Debian.

Expected behavior

The generated email address consists only of characters that are allowed by default in Debian/Ubuntu. I should note that / is a allowed by the standards, but using it may cause extra configuration grief on Debian/Ubuntu and thus may not be worth the trouble.