If you use Gmail then you have a couple of ways besides using the + to make a variation of your email address that will still come to your inbox:
1) Use dots (period or full stop) between letters in the username part of your email address. For example, if your email is abcdefg@gmail.com then a.bcdefg@gmail.com and a.b.c.d.e.f.g@gmail.com also get routed to you.
2) Use @googlemail.com instead of @gmail.com in your email address.
I have a Gmail address and I use these other variations whenever a company rejects email addresses with + in them.
