diff --git a/.github/workflows/bamboo_smtp.yml b/.github/workflows/bamboo_smtp.yml
index 16e89c0..824e0e5 100644
--- a/.github/workflows/bamboo_smtp.yml
+++ b/.github/workflows/bamboo_smtp.yml
@@ -13,14 +13,8 @@ jobs:
     strategy:
       matrix:
         elixir: [1.7.4, 1.8.2, 1.9.1, 1.10.3]
-        otp: [19.3, 20.3, 21.3, 22.0]
+        otp: [20.3, 21.3, 22.0]
         exclude:
-          - elixir: 1.8.2
-            otp: 19.3
-          - elixir: 1.9.1
-            otp: 19.3
-          - elixir: 1.10.3
-            otp: 19.3
           - elixir: 1.10.3
             otp: 20.3
     steps:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index c5c687b..8408b75 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # CHANGELOG
 
+## 3.1.3 - 2021-02-11
+
+- Update `gen_smtp` dependency from 1.0.1 to 1.1.0 ([#171])
+    - This project now requires Erlang/OTP+20
+
 ## 3.1.2 - 2021-01-29
 - Enable Bamboo_smtp to work in ipv6-only environment. Fix issue([#143]).
 
diff --git a/README.md b/README.md
index 4e28a16..ccf1c8d 100644
--- a/README.md
+++ b/README.md
@@ -18,7 +18,7 @@ The package can be installed as:
 
    ```elixir
    def deps do
-     [{:bamboo_smtp, "~> 3.1.2"}]
+     [{:bamboo_smtp, "~> 3.1.3"}]
    end
    ```
 
diff --git a/mix.exs b/mix.exs
index a42c239..d337140 100644
--- a/mix.exs
+++ b/mix.exs
@@ -2,7 +2,7 @@ defmodule BambooSmtp.Mixfile do
   use Mix.Project
 
   @project_url "https://github.com/fewlinesco/bamboo_smtp"
-  @version "3.1.2"
+  @version "3.1.3"
 
   def project do
     [
@@ -29,8 +29,8 @@ defmodule BambooSmtp.Mixfile do
   defp deps do
     [
       # core
-      {:bamboo, "~> 1.6"},
-      {:gen_smtp, "~> 1.0.1"},
+      {:bamboo, "~> 1.7.0"},
+      {:gen_smtp, "~> 1.1.0"},
 
       # dev / test
       {:credo, "~> 1.4.1", only: [:dev, :test]},
diff --git a/mix.lock b/mix.lock
index 2c6734a..dd02bb8 100644
--- a/mix.lock
+++ b/mix.lock
@@ -1,29 +1,29 @@
 %{
-  "bamboo": {:hex, :bamboo, "1.6.0", "adfb583bef028923aae6f22deaea6667290561da1246058556ecaeb0fec5a175", [:mix], [{:hackney, ">= 1.13.0", [hex: :hackney, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:plug, "~> 1.0", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm", "454e67feacbc9b6e00553ce1d2fba003c861e0035600d59b09d6159985b17f9b"},
+  "bamboo": {:hex, :bamboo, "1.7.0", "4b102071e615838aa7329b038b01ca5508dfdf872b5e0bc6aab2c47b3df44f08", [:mix], [{:hackney, ">= 1.15.2", [hex: :hackney, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:mime, "~> 1.4", [hex: :mime, repo: "hexpm", optional: false]}, {:phoenix, "~> 1.1", [hex: :phoenix, repo: "hexpm", optional: true]}, {:plug, "~> 1.0", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm", "b2ec75cf6e570abcb61f736f62ddf156c5d2d821cbba0d12a57df140169fbb96"},
   "bunt": {:hex, :bunt, "0.2.0", "951c6e801e8b1d2cbe58ebbd3e616a869061ddadcc4863d0a2182541acae9a38", [:mix], [], "hexpm", "7af5c7e09fe1d40f76c8e4f9dd2be7cebd83909f31fee7cd0e9eadc567da8353"},
-  "certifi": {:hex, :certifi, "2.5.2", "b7cfeae9d2ed395695dd8201c57a2d019c0c43ecaf8b8bcb9320b40d6662f340", [:rebar3], [{:parse_trans, "~>3.3", [hex: :parse_trans, repo: "hexpm", optional: false]}], "hexpm", "3b3b5f36493004ac3455966991eaf6e768ce9884693d9968055aeeeb1e575040"},
+  "certifi": {:hex, :certifi, "2.5.3", "70bdd7e7188c804f3a30ee0e7c99655bc35d8ac41c23e12325f36ab449b70651", [:rebar3], [{:parse_trans, "~>3.3", [hex: :parse_trans, repo: "hexpm", optional: false]}], "hexpm", "ed516acb3929b101208a9d700062d520f3953da3b6b918d866106ffa980e1c10"},
   "credo": {:hex, :credo, "1.4.1", "16392f1edd2cdb1de9fe4004f5ab0ae612c92e230433968eab00aafd976282fc", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "155f8a2989ad77504de5d8291fa0d41320fdcaa6a1030472e9967f285f8c7692"},
   "earmark": {:hex, :earmark, "1.4.10", "bddce5e8ea37712a5bfb01541be8ba57d3b171d3fa4f80a0be9bcf1db417bcaf", [:mix], [{:earmark_parser, ">= 1.4.10", [hex: :earmark_parser, repo: "hexpm", optional: false]}], "hexpm", "12dbfa80810478e521d3ffb941ad9fbfcbbd7debe94e1341b4c4a1b2411c1c27"},
   "earmark_parser": {:hex, :earmark_parser, "1.4.10", "6603d7a603b9c18d3d20db69921527f82ef09990885ed7525003c7fe7dc86c56", [:mix], [], "hexpm", "8e2d5370b732385db2c9b22215c3f59c84ac7dda7ed7e544d7c459496ae519c0"},
   "ex_doc": {:hex, :ex_doc, "0.23.0", "a069bc9b0bf8efe323ecde8c0d62afc13d308b1fa3d228b65bca5cf8703a529d", [:mix], [{:earmark_parser, "~> 1.4.0", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}], "hexpm", "f5e2c4702468b2fd11b10d39416ddadd2fcdd173ba2a0285ebd92c39827a5a16"},
   "excoveralls": {:hex, :excoveralls, "0.13.3", "edc5f69218f84c2bf61b3609a22ddf1cec0fbf7d1ba79e59f4c16d42ea4347ed", [:mix], [{:hackney, "~> 1.16", [hex: :hackney, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "cc26f48d2f68666380b83d8aafda0fffc65dafcc8d8650358e0b61f6a99b1154"},
-  "gen_smtp": {:hex, :gen_smtp, "1.0.1", "cc3de2898d9136ff02dc78fc8193d4fc997824fc793f5bbbada79ccde94581be", [:rebar3], [{:hut, "1.3.0", [hex: :hut, repo: "hexpm", optional: false]}, {:ranch, "1.6.2", [hex: :ranch, repo: "hexpm", optional: false]}], "hexpm", "341a98dc4dafad9cc1e4426e4988e45b31d3f235fa637408f7579a9b598c0ab6"},
-  "hackney": {:hex, :hackney, "1.16.0", "5096ac8e823e3a441477b2d187e30dd3fff1a82991a806b2003845ce72ce2d84", [:rebar3], [{:certifi, "2.5.2", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "6.0.1", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "1.0.1", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "~>1.1", [hex: :mimerl, repo: "hexpm", optional: false]}, {:parse_trans, "3.3.0", [hex: :parse_trans, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "1.1.6", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}], "hexpm", "3bf0bebbd5d3092a3543b783bf065165fa5d3ad4b899b836810e513064134e18"},
+  "gen_smtp": {:hex, :gen_smtp, "1.1.0", "b0c92138f69e2f73e1eb791075e93e952efcbc231a536740749b02a1a57155a3", [:rebar3], [{:hut, "1.3.0", [hex: :hut, repo: "hexpm", optional: false]}, {:ranch, ">= 1.7.0", [hex: :ranch, repo: "hexpm", optional: false]}], "hexpm", "e53a13c4bb662331bdf4aa47f00982ef49ce2b4e5c703240542cb7b28f23546a"},
+  "hackney": {:hex, :hackney, "1.17.0", "717ea195fd2f898d9fe9f1ce0afcc2621a41ecfe137fae57e7fe6e9484b9aa99", [:rebar3], [{:certifi, "~>2.5", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "~>6.1.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "~>1.0.0", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "~>1.1", [hex: :mimerl, repo: "hexpm", optional: false]}, {:parse_trans, "~>3.3", [hex: :parse_trans, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "~>1.1.0", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}, {:unicode_util_compat, "~>0.7.0", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "64c22225f1ea8855f584720c0e5b3cd14095703af1c9fbc845ba042811dc671c"},
   "hut": {:hex, :hut, "1.3.0", "71f2f054e657c03f959cf1acc43f436ea87580696528ca2a55c8afb1b06c85e7", [:"erlang.mk", :rebar, :rebar3], [], "hexpm", "7e15d28555d8a1f2b5a3a931ec120af0753e4853a4c66053db354f35bf9ab563"},
-  "idna": {:hex, :idna, "6.0.1", "1d038fb2e7668ce41fbf681d2c45902e52b3cb9e9c77b55334353b222c2ee50c", [:rebar3], [{:unicode_util_compat, "0.5.0", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "a02c8a1c4fd601215bb0b0324c8a6986749f807ce35f25449ec9e69758708122"},
+  "idna": {:hex, :idna, "6.1.1", "8a63070e9f7d0c62eb9d9fcb360a7de382448200fbbd1b106cc96d3d8099df8d", [:rebar3], [{:unicode_util_compat, "~>0.7.0", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "92376eb7894412ed19ac475e4a86f7b413c1b9fbb5bd16dccd57934157944cea"},
   "inch_ex": {:hex, :inch_ex, "2.0.0", "24268a9284a1751f2ceda569cd978e1fa394c977c45c331bb52a405de544f4de", [:mix], [{:bunt, "~> 0.2", [hex: :bunt, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "96d0ec5ecac8cf63142d02f16b7ab7152cf0f0f1a185a80161b758383c9399a8"},
   "jason": {:hex, :jason, "1.2.2", "ba43e3f2709fd1aa1dce90aaabfd039d000469c05c56f0b8e31978e03fa39052", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "18a228f5f0058ee183f29f9eae0805c6e59d61c3b006760668d8d18ff0d12179"},
   "makeup": {:hex, :makeup, "1.0.5", "d5a830bc42c9800ce07dd97fa94669dfb93d3bf5fcf6ea7a0c67b2e0e4a7f26c", [:mix], [{:nimble_parsec, "~> 0.5 or ~> 1.0", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "cfa158c02d3f5c0c665d0af11512fed3fba0144cf1aadee0f2ce17747fba2ca9"},
   "makeup_elixir": {:hex, :makeup_elixir, "0.15.0", "98312c9f0d3730fde4049985a1105da5155bfe5c11e47bdc7406d88e01e4219b", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.1", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "75ffa34ab1056b7e24844c90bfc62aaf6f3a37a15faa76b07bc5eba27e4a8b4a"},
   "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [:rebar3], [], "hexpm", "69b09adddc4f74a40716ae54d140f93beb0fb8978d8636eaded0c31b6f099f16"},
-  "mime": {:hex, :mime, "1.4.0", "5066f14944b470286146047d2f73518cf5cca82f8e4815cf35d196b58cf07c47", [:mix], [], "hexpm", "75fa42c4228ea9a23f70f123c74ba7cece6a03b1fd474fe13f6a7a85c6ea4ff6"},
+  "mime": {:hex, :mime, "1.5.0", "203ef35ef3389aae6d361918bf3f952fa17a09e8e43b5aa592b93eba05d0fb8d", [:mix], [], "hexpm", "55a94c0f552249fc1a3dd9cd2d3ab9de9d3c89b559c2bd01121f824834f24746"},
   "mimerl": {:hex, :mimerl, "1.2.0", "67e2d3f571088d5cfd3e550c383094b47159f3eee8ffa08e64106cdf5e981be3", [:rebar3], [], "hexpm", "f278585650aa581986264638ebf698f8bb19df297f66ad91b18910dfc6e19323"},
   "nimble_parsec": {:hex, :nimble_parsec, "1.1.0", "3a6fca1550363552e54c216debb6a9e95bd8d32348938e13de5eda962c0d7f89", [:mix], [], "hexpm", "08eb32d66b706e913ff748f11694b17981c0b04a33ef470e33e11b3d3ac8f54b"},
-  "parse_trans": {:hex, :parse_trans, "3.3.0", "09765507a3c7590a784615cfd421d101aec25098d50b89d7aa1d66646bc571c1", [:rebar3], [], "hexpm", "17ef63abde837ad30680ea7f857dd9e7ced9476cdd7b0394432af4bfc241b960"},
+  "parse_trans": {:hex, :parse_trans, "3.3.1", "16328ab840cc09919bd10dab29e431da3af9e9e7e7e6f0089dd5a2d2820011d8", [:rebar3], [], "hexpm", "07cd9577885f56362d414e8c4c4e6bdf10d43a8767abb92d24cbe8b24c54888b"},
   "plug": {:hex, :plug, "1.11.0", "f17217525597628298998bc3baed9f8ea1fa3f1160aa9871aee6df47a6e4d38e", [:mix], [{:mime, "~> 1.0", [hex: :mime, repo: "hexpm", optional: false]}, {:plug_crypto, "~> 1.1.1 or ~> 1.2", [hex: :plug_crypto, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "2d9c633f0499f9dc5c2fd069161af4e2e7756890b81adcbb2ceaa074e8308876"},
   "plug_crypto": {:hex, :plug_crypto, "1.2.0", "1cb20793aa63a6c619dd18bb33d7a3aa94818e5fd39ad357051a67f26dfa2df6", [:mix], [], "hexpm", "a48b538ae8bf381ffac344520755f3007cc10bd8e90b240af98ea29b69683fc2"},
-  "ranch": {:hex, :ranch, "1.6.2", "6db93c78f411ee033dbb18ba8234c5574883acb9a75af0fb90a9b82ea46afa00", [:rebar3], [], "hexpm", "0b65d1de7f1ebe96feb57803c8d698f7776b663ba10b6dcff34527e4a4f8ff43"},
+  "ranch": {:hex, :ranch, "2.0.0", "fbf3d79661c071543256f9051caf19d65daa6df1cf6824d8f37a49b19a66f703", [:rebar3], [], "hexpm", "c20a4840c7d6623c19812d3a7c828b2f1bd153ef0f124cb69c54fe51d8a42ae0"},
   "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.6", "cf344f5692c82d2cd7554f5ec8fd961548d4fd09e7d22f5b62482e5aeaebd4b0", [:make, :mix, :rebar3], [], "hexpm", "bdb0d2471f453c88ff3908e7686f86f9be327d065cc1ec16fa4540197ea04680"},
   "telemetry": {:hex, :telemetry, "0.4.2", "2808c992455e08d6177322f14d3bdb6b625fbcfd233a73505870d8738a2f4599", [:rebar3], [], "hexpm", "2d1419bd9dda6a206d7b5852179511722e2b18812310d304620c7bd92a13fcef"},
-  "unicode_util_compat": {:hex, :unicode_util_compat, "0.5.0", "8516502659002cec19e244ebd90d312183064be95025a319a6c7e89f4bccd65b", [:rebar3], [], "hexpm", "d48d002e15f5cc105a696cf2f1bbb3fc72b4b770a184d8420c8db20da2674b38"},
+  "unicode_util_compat": {:hex, :unicode_util_compat, "0.7.0", "bc84380c9ab48177092f43ac89e4dfa2c6d62b40b8bd132b1059ecc7232f9a78", [:rebar3], [], "hexpm", "25eee6d67df61960cf6a794239566599b09e17e668d3700247bc498638152521"},
 }