cargo update -p lettre -p lettre_email --aggressive

    Updating bufstream v0.1.3 -> v0.1.4
    Updating cc v1.0.53 -> v1.0.54
    Updating chrono v0.4.9 -> v0.4.11
    Updating lettre v0.9.2 -> v0.9.3
    Updating lettre_email v0.9.2 -> v0.9.4
    Updating num-integer v0.1.41 -> v0.1.42
    Updating num-traits v0.2.10 -> v0.2.11
    Updating openssl-sys v0.9.56 -> v0.9.57
    Updating proc-macro2 v1.0.13 -> v1.0.17
    Updating rand v0.4.2 -> v0.4.6
    Updating serde v1.0.106 -> v1.0.110
    Updating serde_derive v1.0.106 -> v1.0.110
    Updating serde_json v1.0.52 -> v1.0.53
    Updating syn v1.0.22 -> v1.0.27

Author: JohnTitor